按点赞数降序
297 二分
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long #define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head const int N = 1e5 + 5; int a[N], c, n; bool check(int d) { int pre = a[1], cnt = 1; for(int i = 2; i <= n; i++) { if((a[i] - pre) >= d) { pre = a[i]; cnt++; } } return cnt >= c; } int main() { int T; scanf("%d", &T); while(T--) { scanf("%d%d", &n, &c); for (int i = 1; i <= n; i++) scanf("%d", &a[i]); sort(a+1, a+1+n); int l = 1, r = 1e9+5, m = (l+r) >> 1; while(l < r) { if(check(m)) l = m; else r = m - 1; m = (l+r+1) >> 1; //cout << l <<" " << r << endl; } printf("%d ", m); } return 0; }
2 区间素数筛
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long #define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head const int N = 1e5 + 5; bool notp_big[N], notp_small[N]; void prime(LL a, LL b) { mem(notp_big, false); if(a==1) notp_big[0] = true; for (LL i = 2; i*i <= b; i++) { if(!notp_small[i]) { for (LL j = i+i; j*j <= b; j += i) notp_small[j] = true; for (LL j = max(2LL, (a+i-1)/i)*i; j <= b; j += i)notp_big[j-a] = true; } } } int main() { int T, n, m; scanf("%d", &T); while(T--) { scanf("%d%d", &n, &m); prime(n, m); for (int i = n; i <= m; i++) if(!notp_big[i-n])printf("%d ", i); } return 0; }
346 dp 小于5e6预处理，大于5e6递归
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long //#define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head const int N = 5e6+5; int dp[N]; map<int, LL>mp; LL f(int n) { if(n <= 5e6) return dp[n]; else if(mp[n] != 0) return mp[n]; return max((LL)n, f(n/2)+f(n/3)+f(n/4)); } int main() { int n; dp[0]=0; dp[1]=1; for (int i = 2; i < N; i++) { dp[i] = max(i, dp[i/2]+dp[i/3]+dp[i/4]); } while(~ scanf("%d", &n)) { mp.clear(); printf("%lld ", f(n)); } return 0; }
394 dp 注意0的情况
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long //#define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head const int N = 5555; char s[N]; LL dp[N]; int main() { while(~scanf("%s", s+1)) { //printf("%s ", s+1); if(s[1] == '0')break; dp[0] = dp[1] = 1; int n = strlen(s+1); for (int i = 2; i <= n; i++) { if(s[i-1] != '0') { int t = (s[i-1]-'0')*10 + s[i]-'0'; //cout << t << endl; if(t <= 26) { if(s[i] != '0')dp[i] = dp[i-1] + dp[i-2]; else dp[i] = dp[i-2]; } else dp[i] = dp[i-1]; } else dp[i] = dp[i-1]; } printf("%lld ", dp[n]); } return 0; }
1043 线段数区间合并，lv记录这段区间以左端点为起点的最大和，rv同理
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long //#define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head const int N = 5e4 + 5; const int INF = 0x7f7f7f7f; struct Tree { int sum, lv, rv, ans; }tree[N<<2]; void push_up(int rt) { tree[rt].sum = tree[rt<<1].sum + tree[rt<<1|1].sum; tree[rt].lv = max(tree[rt<<1].lv, tree[rt<<1].sum + tree[rt<<1|1].lv); tree[rt].rv = max(tree[rt<<1|1].rv, tree[rt<<1|1].sum + tree[rt<<1].rv); tree[rt].ans = max(tree[rt<<1].rv + tree[rt<<1|1].lv, max(tree[rt<<1].ans, tree[rt<<1|1].ans)); } void build(int rt, int l, int r) { if(l == r) { scanf("%d", &tree[rt].ans); tree[rt].lv = tree[rt].rv = tree[rt].sum = tree[rt].ans; return ; } int m = (l+r) >> 1; build(ls); build(rs); push_up(rt); } Tree query(int L, int R, int rt, int l, int r) { if(L <= l && r <= R) return tree[rt]; int m = (l + r) >> 1; if(R <= m) return query(L, R, ls); else if(L > m) return query(L, R, rs); Tree lft = query(L, R, ls); Tree rit = query(L, R, rs); int sum = lft.sum+rit.sum; int lv = max(lft.lv, lft.sum+rit.lv); int rv = max(rit.rv, rit.sum+lft.rv); int ans = max(lft.rv+rit.lv, max(lft.ans, rit.ans)); return Tree{sum, lv, rv, ans}; } int main() { int n, m, x, y; scanf("%d", &n); build(1, 1, n); scanf("%d", &m); while(m --) { scanf("%d%d", &x, &y); Tree res = query(x, y, 1, 1, n); printf("%d ", res.ans); } return 0; }
6256 普通的逆序数，不过我使用了最近学的方法，从大到小加入位置，跑的比较优秀
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long #define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head const int N = 2e5 + 5; pii a[N]; int bit[N], n; void add(int x, int a) { while(x <= n) bit[x] += a, x += x&-x; } int query(int x) { int ans = 0; while(x) ans += bit[x], x -= x&-x; return ans; } int main() { int T; scanf("%d", &T); while(T--) { scanf("%d", &n); for (int i = 1; i <= n; i++) { scanf("%d", &a[i].fi); a[i].se = i; } sort(a+1, a+1+n); mem(bit, 0); LL ans = 0; for(int i = n; i >= 1; i--) { ans += query(a[i].se); //cout <<".............."<< ans << endl; add(a[i].se, 1); } printf("%lld ", ans); } return 0; }
5 纯暴力，从中间加
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long #define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head const int N = 1e6 + 10; char s[N]; int num[N], t[N], n; bool cmp() { for(int i = 1;i <= n; i++) { if(t[i] < num[i]) return true; else if(t[i] > num[i]) return false; } return true; } int main() { int T; scanf("%d", &T); while(T--) { scanf("%s", s+1); n = strlen(s+1); for (int i = 1; i <= n; i++) num[i] = s[i] - '0'; for (int i = 1; i <= (n+1)/2; i++) { t[i] = t[n-i+1] = num[i]; } if(n==1) { if(num[1] == 9) printf("11 "); else printf("%d ", num[1]+1); continue; } while(cmp()) { t[(n+1)/2]++; for (int i = (n+1)/2; i >= 2; i--) { t[i-1] += t[i]/10; t[i] %= 10; } for (int i = 1; i <= (n+1)/2; i++) { t[n-i+1] = t[i]; } } for (int i = 1; i < n; i++) printf("%d", t[i]); if(t[n] == 10) printf("1 ");//样例999 else printf("%d ", t[n]); } return 0; }
8002 树状数组区间更新，区间查询
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long //#define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head const int N = 1e5 + 5; int a[N], n; LL sum[N], c1[N], c2[N]; void add(int x, int a) { LL t = x; while(x <= n) c1[x] += a, c2[x] += t*a, x += x&-x; } LL query(int x) { LL ans = 0; LL t = x; while(x) ans += (t+1) * c1[x] - c2[x], x -= x&-x; return ans; } int main() { int T, op, c, p, q, v; scanf("%d", &T); while(T--) { mem(c1, 0); mem(c2, 0); scanf("%d%d", &n, &c); while(c--) { scanf("%d", &op); if(op == 1) { scanf("%d%d", &p, &q); printf("%lld ", query(q) - query(p-1)); } else { scanf("%d%d%d", &p, &q, &v); add(p, v); add(q+1, -v); } } } return 0; }
3267 离线+树状数组，每次保证这段区间每个数只更新一次，或者主席树(不会，等我学了在a)
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long //#define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head const int N = 3e5 + 5, M = 2e5 + 5; int a[N], nxt[N], bit[N], mp[M*5], n; struct node { int l, r, id; bool operator < (const node & t) const { if(l == t.l) return r < t.r; else return l < t.l; } }Q[M]; int ans[N]; void add(int x, int a) { while(x <= n) bit[x] += a, x += x&-x; } int query(int x) { int ans = 0; while(x) ans += bit[x], x -= x&-x; return ans; } int main() { int q; scanf("%d", &n); for (int i = 1; i <= n; i++) scanf("%d", &a[i]); for (int i = 1; i <= n; i++) { if(mp[a[i]] == 0) { add(i, 1); mp[a[i]] = i; } } mem(mp, 0); for (int i = n; i; i--) { if(mp[a[i]] == 0) { nxt[i] = n+1; mp[a[i]] = i; } else { nxt[i] = mp[a[i]]; mp[a[i]] = i; } } scanf("%d", &q); for (int i = 0; i < q; i++) scanf("%d%d", &Q[i].l, &Q[i].r), Q[i].id = i; sort(Q, Q+q); int t = 1; for (int i = 0; i < q; i++) { while(t <= n && t < Q[i].l) add(nxt[t++], 1); ans[Q[i].id] = query(Q[i].r) - query(Q[i].l-1); } for (int i = 0; i < q; i++) printf("%d ", ans[i]); return 0; }
主席树（2019.3更新），感觉这个没有离线优秀，不过思想还行，就当练练可持久化
#pragma GCC optimize(2) #pragma GCC optimize(3) #pragma GCC optimize(4) #include<iostream> #include<cstdio> #include<vector> #include<climits> using namespace std; #define y1 y11 #define fi first #define se second #define pi acos(-1.0) #define LL long long //#define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pli pair<LL, int> #define pii pair<int, int> #define piii pair<pii, int> #define pdd pair<double, double> #define mem(a, b) memset(a, b, sizeof(a)) #define debug(x) cerr << #x << " = " << x << " "; #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); //head const int N = 3e4 + 5, M = 1e6 + 5; int root[N], lson[M], rson[M], tree[M], tot = 0; void build(int &x, int l, int r) { x = ++tot; if(l == r) return ; int m = l+r >> 1; build(lson[x], l, m); build(rson[x], m+1, r); tree[x] = tree[lson[x]] + tree[rson[x]]; } void update(int old, int &x, int p, int v, int l, int r) { x = ++tot; lson[x] = lson[old], rson[x] = rson[old], tree[x] = tree[old] + v; if(l == r) return ; int m = l+r >> 1; if(p <= m) update(lson[x], lson[x], p, v, l, m); else update(rson[x], rson[x], p, v, m+1, r); } int query(int L, int R, int x, int l, int r) { if(L <= l && r <= R) return tree[x]; int m = l+r >> 1, ans = 0; if(L <= m) ans += query(L, R, lson[x], l, m); if(R > m ) ans += query(L, R, rson[x], m+1, r); return ans; } int n, a, mp[M], tmp, q, l, r; int main() { scanf("%d", &n); build(root[0], 1, n); for (int i = 1; i <= n; ++i) { scanf("%d", &a); if(mp[a]) { update(root[i-1], tmp, mp[a], -1, 1, n); update(tmp, root[i], i, 1, 1, n); } else update(root[i-1], root[i], i, 1, 1, n); mp[a] = i; } scanf("%d", &q); while(q--) { scanf("%d %d", &l, &r); printf("%d ", query(l, r, root[r], 1, n)); } return 0; }
1437 树的直径，两遍dfs
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long //#define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head const int N = 1e4 + 5; vector<int>g[N]; int mx = 0, ed = 0; void dfs(int o, int u, int st) { if(st > mx) { mx = st; ed = u; } for (int i = 0; i < g[u].size(); i++) { if(g[u][i] != o) { dfs(u, g[u][i], st+1); } } } int main() { int n, u, v; scanf("%d", &n); for (int i = 0; i < n-1; i++) { scanf("%d%d", &u, &v); g[u].pb(v); g[v].pb(u); } dfs(0, 1, 0); dfs(0, ed, 0); printf("%d ", mx); return 0; }
1436 dfs
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long //#define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head const int N = 1e4 + 5; vector<int>g[N]; bool vis[N]; bool f = true; void dfs(int o, int u) { vis[u] = true; for (int i = 0; i < g[u].size(); i++) { if(g[u][i] != o) { if(!vis[g[u][i]])dfs(u, g[u][i]); else f = false; } } } int main() { int n, m, u, v; scanf("%d%d", &n, &m); for (int i = 0; i < m; i++) { scanf("%d%d", &u, &v); g[u].pb(v); g[v].pb(u); } dfs(0, 1); for (int i = 1; i <= n; i++) if(!vis[i]) f = false; if(f) puts("YES"); else puts("NO"); return 0; }
6219 普通dp, 与LCS相似
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long //#define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head const int N = 2e3 + 5; char s[N], t[N]; int dp[N][N]; int main() { int T; scanf("%d", &T); while(T--) { scanf("%s", s+1); scanf("%s", t+1); int n = strlen(s+1), m = strlen(t+1); for (int i = 0; i <= n; i++) { for (int j = 0; j <= m; j++) { if(i||j){ if(i == 0) dp[i][j] = j; else if(j == 0) dp[i][j] = i; else if(s[i] == t[j]) dp[i][j] = dp[i-1][j-1]; else dp[i][j] = min(dp[i-1][j-1]+1, min(dp[i-1][j]+1, dp[i][j-1]+1)); } } } printf("%d ", dp[n][m]); } return 0; }
3923 普通dp
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long //#define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head const int N = 105; int a[N][N], dp[N][N]; int main() { int T, n, m; scanf("%d", &T); while(T--) { scanf("%d%d", &n, &m); for (int i = 1; i <= n; i++) { for (int j = 1; j <= m; j++) { scanf("%d", &a[i][j]); } } mem(dp, 0); for (int i = 1; i <= m; i++) dp[1][i] = a[1][i]; for (int i = 2; i <= n; i++) { for (int j = 1; j <= m; j++) { dp[i][j] = max(dp[i-1][j], max(dp[i-1][j-1], dp[i-1][j+1])) + a[i][j]; } } int ans = 0; for (int i = 1; i <= m; i++) ans = max(ans, dp[n][i]); printf("%d ", ans); } return 0; }
95 栈模拟
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long //#define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head stack<int>s; int main() { int n, t; while(~scanf("%d", &n) && n) { while(!s.empty()) s.pop(); int now = 1; for (int i = 1; i <= n; i++) { scanf("%d", &t); if(t == now) now++; else { s.push(t); } while(!s.empty() && s.top() == now) { s.pop(); now++; } } //cout << now << endl; if(now == n+1) puts("yes"); else puts("no"); } return 0; }
1021 原串与反串的LCS就是原串的最长回文子序列
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long //#define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head const int N = 6e3 + 105; char s[N], t[N]; int dp[N][N]; int main() { int T; scanf("%d", &T); while(T--) { scanf("%s", s+1); int n = strlen(s+1); for (int i = 1; i <= n; i++) t[i] = s[n-i+1]; for (int i = 1; i <= n; i++) { for (int j = 1; j <= n; j++) { if(s[i] == t[j]) dp[i][j] = max(dp[i-1][j-1]+1, max(dp[i-1][j], dp[i][j-1])); else dp[i][j] = max(dp[i-1][j], dp[i][j-1]); } } printf("%d ", n-dp[n][n]); } return 0; }
14930 记忆化搜索
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long //#define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head const int N = 1e4 + 5; LL dp[N][2]; int a[N], n; LL dfs(int pos, int sta) { if(pos == n) { if(sta == 0) return 0; else return a[n]; } if(~dp[pos][sta]) return dp[pos][sta]; if(sta == 1) return dp[pos][sta] = a[pos] + dfs(pos+1, 0); else return dp[pos][sta] = max(dfs(pos+1, 1), dfs(pos+1, 0)); } int main() { int T; scanf("%d", &T); for (int cs = 1; cs <= T; cs++) { scanf("%d", &n); for (int i = 1; i <= n; i++) scanf("%d", &a[i]); mem(dp, -1); LL ans = max(dfs(1, 0), dfs(1, 1)); printf("Case %d: %lld ", cs, ans); } return 0; }
1841 bfs
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long #define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head const int N = 1e4 + 5; bool notp[N]; bool vis[N]; int d[10], dd[10]; int p[10] = {0, 1, 10, 100, 1000}; int a, b, ans; bool bfs() { mem(vis, false); queue<pii>q; q.push(mp(a, 0)); vis[a] = true; while(!q.empty()) { pii p = q.front(); q.pop(); int t = p.fi; if(t == b) { ans = p.se; return true; } for (int i = 1; i <= 4; i++) { d[i] = t%10; t /= 10; } for (int i = 1; i <= 4; i++) { int t = 0; if(i == 4) t = 1; for (int j = t; j < 10; j++) { if(j == d[i]) continue; for (int k = 1; k <= 4; k++) { if(k == i) continue; dd[k] = d[k]; } dd[i] = j; int n = 0; for (int k = 4; k >=1; k--) n = n *10 + dd[k]; if(!notp[n] && !vis[n]) { vis[n] = true; q.push(mp(n, p.se+1)); } } } } return false; } int main() { int T; scanf("%d", &T); for (int i = 2; i < N; i++) { if(!notp[i]) { for (int j = i+i; j < N ;j += i) notp[j] = true; } } for (int cs = 1; cs <= T; cs++) { scanf("%d%d", &a, &b); if(bfs())printf("%d ", ans); else printf("Impossible "); } return 0; }
97 背包dp
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long #define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head const int N = 555; int dp[N], c[N], v[N]; int main() { int n, m; while(~scanf("%d%d", &n, &m)) { if(!n && !m) return 0; int ans; mem(dp, 0); for (int i = 1; i <= m; i++) scanf("%d%d", &c[i], &v[i]); for (int i = 1; i <= m; i++) { for (int j = n; j >= c[i]; j--) { dp[j] = max(dp[j-c[i]]+v[i], dp[j]); } } for (int i = n; i >= 0; i--) if(dp[i] == dp[n]) ans = i; printf("%d %d ", ans, dp[n]); } return 0; }
740 区间dp， 小区间推大区间，dp[i][j] = max(dp[i+1][j] + (n+i-j) * a[i], dp[i][j-1] + (n+i-j) * a[j])
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long #define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head const int N = 2e3 + 5; int dp[N][N], a[N]; int main() { int n; scanf("%d", &n); for (int i = 1; i <= n; i++) scanf("%d", &a[i]); for (int i = n; i >=1; i--) { dp[i][i] = a[i] * n; for (int j = i+1; j <= n; j++) { dp[i][j] = max(dp[i+1][j] + (n+i-j) * a[i], dp[i][j-1] + (n+i-j) * a[j]); } } printf("%d ", dp[1][n]); return 0; }
206 每次向外扩展一次，做多扩展max(n,m)次，所以复杂度为max(n,m)*n*m
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long #define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head const int N = 222; const int INF = 0x3f3f3f3f; char s[N][N]; int ans[N][N]; int dir[4][2] = {0, 1, 1, 0, 0, -1, -1, 0}; int main() { int T, n, m; scanf("%d", &T); while(T--) { scanf("%d%d", &n, &m); mem(ans, INF); for (int i = 1; i <= n; i++) scanf("%s", s[i]+1); for (int i = 1; i <= n; i++) { for (int j = 1; j <= m; j++) { if(s[i][j] == '1') ans[i][j] = 0; } } for (int i = 1; i <= max(n, m); i++) { for (int j = 1; j <= n; j++) { for (int k = 1; k <= m; k++) { if(ans[j][k] != INF) for (int l = 0; l < 4; l++) { int x = j + dir[l][0]; int y = k + dir[l][1]; if(1 <= x && x <= n && 1 <= y && y <= m) { ans[x][y] = min(ans[x][y], ans[j][k] + 1); } } } } } for (int i = 1; i <= n; i++) { for (int j = 1; j <= m; j++) { printf("%d%c", ans[i][j], " "[j==m]); } } } return 0; }
9861 双指针
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long #define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head const int N = 3e5 + 5; int a[N]; int main() { int n, m; scanf("%d%d", &n, &m); for (int i = 1; i <= n; i++) { scanf("%d", &a[i]); } int ans = 0; int l = 0, r = 0, sum = 0; while(true) { while(sum <= m && r < n) { ans = max(ans, sum); sum += a[++r]; } if(sum <= m) ans = max(ans, sum); while(sum > m) { sum -= a[++l]; } if(sum <= m) ans = max(ans, sum); if(r == n) break; } printf("%d ", ans); return 0; }
3377 带权并查集或普通并查集
带权
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long #define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head const int N = 2e3 + 5; int fa[N], rnk[N]; void init(int n) { for (int i = 0; i <= n; i++) { fa[i] = i; rnk[i] = 0; } } int find(int x) { if(fa[x] == x) return x; else{ int tmp = fa[x]; fa[x] = find(fa[x]); rnk[x] = (rnk[x] + rnk[tmp]) % 2; return fa[x]; } } void merge(int x, int y) { int rx = find(x), ry = find(y); if(rx == ry) return; fa[rx] = ry; rnk[rx] = (rnk[y] + 1 -rnk[x]) % 2; } int main() { int T, n, m, u, v; scanf("%d", &T); for (int cs = 1; cs <= T; cs++) { scanf("%d%d", &n, &m); printf("Scenario #%d: ", cs); init(n); bool f = false; for (int i = 0; i < m; i++) { scanf("%d%d", &u, &v); if(find(u) == find(v) && rnk[u] == rnk[v]) f = true; else merge(u, v); } if(f) printf("Suspicious bugs found! "); else printf("No suspicious bugs found! "); } return 0; }
普通
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long #define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head const int N = 2e3 + 5; int fa[N*2]; void init(int n) { for (int i = 0; i <= n*2; i++) { fa[i] = i; } } int find(int x) { if(x == fa[x]) return x; else return fa[x] = find(fa[x]); } void merge(int x, int y) { int rx = find(x), ry = find(y); if(rx == ry) return; fa[rx] = ry; } int main() { int T, n, m, u, v; scanf("%d", &T); for (int cs = 1; cs <= T; cs++) { scanf("%d%d", &n, &m); printf("Scenario #%d: ", cs); init(n); bool f = false; for (int i = 0; i < m; i++) { scanf("%d%d", &u, &v); if(find(u) == find(v) || find(u+n) == find(v+n)) f = true; else merge(u, v+n), merge(v, u+n); } if(f) printf("Suspicious bugs found! "); else printf("No suspicious bugs found! "); } return 0; }
10582 multiset维护（注意删一个元素需要s.erase(s.find(x)),否则会把所有的x都会删掉），顺便复习了一下st表，用st表写了一发
multiset
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long #define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head const int N = 1e6 + 5; int a[N]; multiset<int>s; int main() { int n, k; scanf("%d", &n); for (int i = 1; i <= n; ++i) scanf("%d", &a[i]); scanf("%d", &k); for (int i = 1; i < k; i++) s.insert(a[i]); for (int i = k; i <= n; i++) { s.insert(a[i]); auto it = s.end(); it --; printf("%d%c", *it, " "[i==n]); s.erase(s.find(a[i-k+1])); } return 0; }
st表
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long #define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head const int N = 1e6 + 5; int a[N], st[N][20]; int query(int l, int r) { int k = floor(log(r-l+1)/log(2)); return max(st[l][k], st[r - (1 << k) + 1][k]); } int main() { int n, k; scanf("%d", &n); for (int i = 1; i <= n; ++i) scanf("%d", &a[i]); scanf("%d", &k); for (int i = n; i >= 1; i--) { st[i][0] = a[i]; for (int j = 1; j + (1 << j-1) <= n; j++) { st[i][j] = max(st[i][j-1], st[i+(1 << j-1)][j-1]); } } for (int i = k; i <= n; i++) printf("%d%c", query(i-k+1, i), " "[i==n]); return 0; }
4 stack
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long #define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head const int N = 1e4 + 5; char s[N]; bool is(char c) { if(c == '+' || c == '-' || c == '*' || c == '/' || c == '^') return true; else return false; } int main() { int T; scanf("%d", &T); while(T--) { scanf("%s", s+1); int n = strlen(s+1); stack<char>st; for (int i = 1; i <= n; i++) { if(isalpha(s[i])) putchar(s[i]); else if(is(s[i])) st.push(s[i]); else if(s[i] == ')') putchar(st.top()), st.pop(); } puts(""); } return 0; }
61 线段树区间合并，左区间的左括号和右区间的有括号抵消，看有没有剩下的没匹配的括号
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long #define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head const int N = 3e4 + 5; char s[N]; struct sg_tree{ int L[N<<2], R[N<<2]; void push_up(int rt) { L[rt] = L[rt<<1] + L[rt<<1|1] - min(L[rt<<1], R[rt<<1|1]); R[rt] = R[rt<<1] + R[rt<<1|1] - min(L[rt<<1], R[rt<<1|1]); } void build(int rt, int l,int r) { if(l == r) { if(s[l] == '(') L[rt] = 1, R[rt] = 0; else R[rt] = 1, L[rt] = 0; return ; } int m = (l+r) >> 1; build(ls); build(rs); push_up(rt); } void update(int p, int rt, int l, int r) { if(l == r) { L[rt] ^= 1; R[rt] ^= 1; return ; } int m = (l+r) >> 1; if(p <= m) update(p, ls); else update(p, rs); push_up(rt); } }sg; int main() { int n, m, t, cs = 0; while(~ scanf("%d", &n)) { scanf("%s", s+1); scanf("%d", &m); printf("Test %d: ", ++cs); sg.build(1, 1, n); while(m--) { scanf("%d", &t); if(!t) { if(sg.L[1] || sg.R[1]) printf("NO "); else printf("YES "); } else sg.update(t, 1, 1, n); } } return 0; }
1716 线段树区间合并，同1043
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long //#define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head const int N = 5e4 + 5; const int INF = 0x7f7f7f7f; struct Tree { int sum, lv, rv, ans; }tree[N<<2]; void push_up(int rt) { tree[rt].sum = tree[rt<<1].sum + tree[rt<<1|1].sum; tree[rt].lv = max(tree[rt<<1].lv, tree[rt<<1].sum + tree[rt<<1|1].lv); tree[rt].rv = max(tree[rt<<1|1].rv, tree[rt<<1|1].sum + tree[rt<<1].rv); tree[rt].ans = max(tree[rt<<1].rv + tree[rt<<1|1].lv, max(tree[rt<<1].ans, tree[rt<<1|1].ans)); } void build(int rt, int l, int r) { if(l == r) { scanf("%d", &tree[rt].ans); tree[rt].lv = tree[rt].rv = tree[rt].sum = tree[rt].ans; return ; } int m = (l+r) >> 1; build(ls); build(rs); push_up(rt); } void update(int p, int x, int rt, int l ,int r) { if(l == r) { tree[rt].lv = tree[rt].rv = tree[rt].sum = tree[rt].ans = x; return ; } int m = (l+r) >> 1; if(p <= m) update(p, x, ls); else update(p, x, rs); push_up(rt); } Tree query(int L, int R, int rt, int l, int r) { if(L <= l && r <= R) return tree[rt]; int m = (l + r) >> 1; if(R <= m) return query(L, R, ls); else if(L > m) return query(L, R, rs); Tree lft = query(L, R, ls); Tree rit = query(L, R, rs); int sum = lft.sum+rit.sum; int lv = max(lft.lv, lft.sum+rit.lv); int rv = max(rit.rv, rit.sum+lft.rv); int ans = max(lft.rv+rit.lv, max(lft.ans, rit.ans)); return Tree{sum, lv, rv, ans}; } int main() { int n, m, x, y, op; scanf("%d", &n); build(1, 1, n); scanf("%d", &m); while(m --) { scanf("%d%d%d", &op, &x, &y); if(op) { Tree res = query(x, y, 1, 1, n); printf("%d ", res.ans); } else { update(x, y, 1, 1, n); } } return 0; }
345 区间dp,经典石子归并问题
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long #define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head const int N = 105; const int INF = 0x3f3f3f3f; int a[N], sum[N], dp[N][N]; int main() { int n; while(~scanf("%d", &n)) { for (int i = 1; i <= n; i++) scanf("%d", &a[i]); for (int i = 1; i <= n; i++) sum[i] = sum[i-1] + a[i]; for (int l = 2; l <= n; l ++) { for (int i = 1; i+l-1 <= n; i++) { int j = i+l-1; dp[i][j] = INF; for (int k = i; k < j; k++) { dp[i][j] = min(dp[i][j], dp[i][k] + dp[k+1][j] + ((sum[k]-sum[i-1])%100) * ((sum[j]-sum[k])%100)); } } } printf("%d ", dp[1][n]); } return 0; }
4580 折半枚举
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long #define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head const int N = 105, M = 1e6 + 10; int a[N], b[M]; int main() { int n; scanf("%d", &n); for (int i = 1; i <= n; i++) scanf("%d", &a[i]); int cnt = 0; for (int i = 1; i <= n; i++) { for (int j = 1; j <= n; j++) { for (int k = 1; k <= n; k++) { b[++cnt] = a[i] * a[j] + a[k]; } } } sort(b+1, b+1+cnt); LL ans = 0; for (int i = 1; i <= n; i++) { for (int j = 1; j <= n; j++) { for (int k = 1; k <= n; k++) { if(a[i] != 0) { int t1 = lower_bound(b+1, b+1+cnt, a[i]*(a[j]+a[k])) - b; int t2 = upper_bound(b+1, b+1+cnt, a[i]*(a[j]+a[k])) - b; ans += t2-t1; } } } } printf("%d ", ans); return 0; }
302 数学
#include<iostream> #include<cstdio> #include<cstring> #include<vector> #include<algorithm> #include<cmath> #include<vector> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long #define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head int main() { int T, n; scanf("%d", &T); while(T--) { scanf("%d", &n); int nn = n; int t = sqrt(2*n); t++; if(t*(t-1)/2 >= n) t--; n -= t*(t-1)/2; if(t%2==0)printf("TERM %d IS %d/%d ", nn, n, t-n+1); else printf("TERM %d IS %d/%d ", nn, t-n+1, n); } return 0; }
423 状压dp，一开始写了个n*n*(1<<n)，后来发现每次不用枚举每个状态，只需枚举到上一行为止的所有状态就可以了，开个二维vector滚动保存状态，暴力水过？
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long //#define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head const int N = 22; LL dp[(1<<20) + 5][N]; int a[N][N]; bool vis[(1<<20) + 5]; vector<int>sta[2]; int main() { int T, n; scanf("%d", &T); while(T--) { scanf("%d", &n); for (int i = 1; i <= n; i++) { for (int j = 1; j <= n; j++) scanf("%d", &a[i][j]); } mem(dp, 0); dp[0][0] = 1; int cur = 0; sta[0].clear(); sta[1].clear(); sta[cur].pb(0); for (int i = 1; i <= n; i++) { cur ^= 1; sta[cur].clear(); mem(vis, false); for (int j = 1; j <= n; j++) { if(a[i][j]) { for (int k = 0; k < sta[1-cur].size(); k++) { if(!(sta[1-cur][k] & (1 << (j-1)))) { dp[sta[1-cur][k]|(1 << (j-1))][i] += dp[sta[1-cur][k]][i-1]; if(!vis[sta[1-cur][k]|(1 << (j-1))])sta[cur].pb(sta[1-cur][k]|(1 << (j-1))), vis[sta[1-cur][k]|(1 << (j-1))] = true; } } } } } printf("%lld ", dp[(1<<n)-1][n]); } return 0; }
3266 离线+树状数组，先按询问的k排序，然后把从大到小（我的代码是从小到大，求的是小于等与k的）加入这些数的位置，然后只需要维护前缀和就可以了
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long //#define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head const int N = 3e4 + 5, M = 2e5 + 5; int id[N], a[N], bit[N], ans[M], n; struct node { int l, r, k, id; bool operator < (const node & t) const { return k < t.k; } }b[M]; bool cmp(int x, int y) { return a[x] < a[y]; } void add(int x, int a) { while(x <= n) bit[x] += a, x += x&-x; } int query(int x) { int ans = 0; while(x) ans += bit[x], x -= x&-x; return ans; } int main() { int q; scanf("%d", &n); for (int i = 1; i <= n; i++) scanf("%d", &a[i]), id[i] = i; scanf("%d", &q); for (int i = 1; i <= q; i++) scanf("%d%d%d", &b[i].l, &b[i].r, &b[i].k), b[i].id = i; sort(b+1, b+1+q); sort(id+1, id+1+n, cmp); int t = 1; for (int i = 1; i <= q; i++) { while(t <= n && a[id[t]] <= b[i].k) add(id[t], 1), t++; ans[b[i].id] = b[i].r - b[i].l + 1 - query(b[i].r) + query(b[i].l-1); } for (int i = 1; i <= q; i++) printf("%d ", ans[i]); return 0; }
3946 线段树每个节点开个vector, 然后二分求区间第k大，单次询问复杂度（logn)^3，二分一个logn，线段树一个logn，每个节点二分一个logn
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long //#define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head const int N = 1e5 + 5; int a[N]; vector<int>vc[N<<2]; vector<int>node; void build(int rt, int l, int r) { if(l == r) { scanf("%d", &a[l]); vc[rt].pb(a[l]); return ; } int m = (l+r) >> 1; build(ls); build(rs); for (int i = l; i <= r; i++) vc[rt].pb(a[i]); sort(vc[rt].begin(), vc[rt].end()); } void query(int L, int R, int rt, int l, int r) { if(L <= l && r <= R) { node.pb(rt); return ; } int m = (l+r) >> 1; if(L <= m) query(L, R, ls); if(R > m) query(L, R, rs); } int cal(int x) { int ans = 0; for (int i = 0; i < node.size(); i++) { ans += lower_bound(vc[node[i]].begin(), vc[node[i]].end(), x) - vc[node[i]].begin(); } return ans; } int main() { int n, m, l, r, k; scanf("%d%d", &n, &m); build(1, 1, n); sort(a+1, a+1+n); while(m--) { scanf("%d%d%d", &l, &r, &k); node.clear(); query(l, r, 1, 1, n); l = 1, r = n; int md = (l+r+1) >> 1; while(l < r) { int cnt = cal(a[md]); if(cnt < k) l = md; else r = md - 1; md = (l+r+1) >> 1; } printf("%d ", a[md]); } return 0; }
16487 差分数组
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long //#define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head const int N = 1e4 + 5; int a[N]; int main() { int T, n, m, q, v, l, r; scanf("%d", &T); while(T--) { scanf("%d%d", &n, &m); mem(a, 0); for (int i = 1; i <= m; i++) scanf("%d%d%d", &l, &r, &v), l++, r++, a[l] += v, a[r+1] -= v; for (int i = 1; i <= n; i++) a[i] += a[i-1]; scanf("%d", &q); for (int i = 1; i <= q; i++) scanf("%d", &l), printf("%d ", a[l+1]); } return 0; }
4300 暴力水题
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long //#define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head int main() { int n; scanf("%d", &n); int ans = 0; for (int i = 1; i <= n; i++) { for (int j = 1; j * j <= i; j++) { if(i%j == 0) ans++; } } printf("%d ", ans); return 0; }
14932 lca水题
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long //#define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head const int N = 1e3 + 5; int anc[N][15], deep[N]; vector<int>g[N]; bool vis[N]; void dfs(int o, int u) { deep[u] = deep[o] + 1; for (int i = 0; i < g[u].size(); i++) { anc[g[u][i]][0] = u; for (int j = 1; j < 15; j++) anc[g[u][i]][j] = anc[anc[g[u][i]][j-1]][j-1]; dfs(u, g[u][i]); } } int lca(int u, int v) { if(deep[u] > deep[v]) swap(u, v); for (int i = 14; i >= 0; i--) if(deep[anc[v][i]] >= deep[u]) v = anc[v][i]; if(u == v) return u; for (int i = 14; i >= 0; i--) if(anc[u][i] != anc[v][i]) u = anc[u][i], v= anc[v][i]; return anc[u][0]; } int main() { int T, n, t, u, v, m; scanf("%d", &T); for (int cs = 1; cs <= T; cs++) { mem(vis, false); mem(deep, 0); scanf("%d", &n); for (int i = 1; i <= n; i++) g[i].clear(); for (int i = 1; i <= n; i++) { scanf("%d", &t); while(t--) scanf("%d", &u), vis[u] = true, g[i].pb(u); } int rt = 0; for (int i = 1; i <= n; i++) if(!vis[i]) rt = i; dfs(0, rt); scanf("%d", &m); printf("Case %d: ", cs); while(m--) { scanf("%d%d", &u, &v); printf("%d ", lca(u, v)); } } return 0; }
32 kmp 或者 字符串hash
kmp
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long //#define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head const int N = 1e6 + 5; const int MOD = 1e9 + 7; int nxt[N]; char a[N], b[N]; vector<int>ans; int main() { int n, m; while(~scanf("%d", &n)){ scanf("%s", a); scanf("%s", b); m = strlen(b); nxt[0] = -1; for (int i = 1; i < n; i++) { int j = nxt[i-1]; while(a[j+1] != a[i] && j >= 0) j = nxt[j]; if(a[j+1] == a[i]) nxt[i] = j+1; else nxt[i] = -1; } int i = 0, j = 0; ans.clear(); while(j < m) { if(b[j] == a[i]) { i++; j++; if(i == n) ans.pb(j - n), i = nxt[i-1]+1; } else { if(i == 0) j++; else i = nxt[i-1]+1; } } if(ans.size() == 0) puts(""); else { for (int i = 0; i < ans.size(); i++) printf("%d ", ans[i]); } } return 0; }
字符串hash
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long //#define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head const int N = 1e6 + 5; const int MOD = 1e9 + 7; const int base = 23; char a[N], b[N]; int H[N], p[N]; int get_H(int l, int r) { return (H[r] - 1LL * H[l-1] * p[r-l+1] % MOD + MOD)%MOD; } vector<int>ans; int main() { int n, m; p[0] = 1; for (int i = 1; i < N; i++)p[i] = (1LL * p[i-1] * base)%MOD; while(~scanf("%d", &n)){ scanf("%s", a+1); int f = 0; for (int i = 1; i <= n; i++) f = (1LL * f * base + a[i] - 'a')%MOD; scanf("%s", b+1); m = strlen(b+1); for (int i = 1; i <= m; i++) H[i] = (1LL * H[i-1] * base + (b[i] - 'a'))%MOD; ans.clear(); for (int i = 1; i+n-1 <= m; i++) { if(get_H(i, i+n-1) == f) ans.pb(i); } if(ans.size() == 0) puts(""); else { for (int i = 0; i < ans.size(); i++) printf("%d ", ans[i]-1); } } return 0; }
我的傻逼写法：离线+指针，复杂度：Maxa * log(a) + n
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long //#define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head const int N = 1e5 + 5; pii Q[N]; int ans[N]; int main() { int T; scanf("%d", &T); for (int i = 1; i <= T; i++) scanf("%d", &Q[i].fi), Q[i].se = i; sort(Q+1, Q+1+T); int l = 0, c2 = 0, c5 = 0; for (int i = 1; i <= T; i++) { while(l < Q[i].fi) { l++; int t = l; while(t%2 == 0) c2++, t /= 2; while(t%5 == 0) c5++, t /= 5; } ans[Q[i].se] = min(c2, c5); } for (int i = 1; i <= T; i++) printf("%d ", ans[i]); return 0; }
正解：数学
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long //#define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head int main() { int T, n; scanf("%d", &T); for (int i = 1; i <= T; i++) { scanf("%d", &n); int ans = 0; for (LL i = 5; i <= n; i *= 5) ans += n/i; printf("%d ", ans); } return 0; }
7742 水题
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long //#define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head const int N = 5e5 + 5; int a[N]; int main() { int n; scanf("%d", &n); for (int i = 1; i <= n; i++) scanf("%d", &a[i]); sort(a+1, a+1+n); int c = 0; for (int i = 1; i <= n; i++) { if(a[i] != a[i-1]) { if(c == 1) return 0 * printf("%d ", a[i-1]); c = 1; } else c++; } if(c == 1) printf("%d ", a[n]); return 0; }
54 java大数
import java.math.*; import java.util.*; public class Main { public static void main(String[] args) { Scanner reader = new Scanner(System.in); BigInteger d = new BigInteger("2"); while(reader.hasNext()){ BigInteger a = reader.nextBigInteger(); BigInteger b = reader.nextBigInteger(); BigInteger c = a.subtract(b); c = c.divide(d); System.out.println(c.add(b)); System.out.println(c); } } }
3442 快速幂
#include<bits/stdc++.h> using namespace std; #define LL long long LL q_pow(LL n, LL k) { LL ans = 1; while(k) { if(k&1) ans = (ans * n) % 10; n = (n*n) % 10; k >>= 1; } return ans; } int main() { int T; LL a, b; scanf("%d", &T); while(T--) { scanf("%lld%lld", &a, &b); printf("%lld ", q_pow(a, b)); } return 0; }
11515 贪心，每次取这个位置之后能达到的最近的位置，先把每个l和r标记为a[l] = r，然后求个后缀最小值，预处理或者树状数组都可以
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long #define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head const int N = 1e5 + 5, M = 1e6 + 5; const int INF = 0x3f3f3f3f; pii a[N]; int b[M], bit[M]; int mx; void add(int x, int a) { while(x) bit[x] = min(bit[x], a), x -= x&-x; } int query(int x) { int ans = INF; while(x <= mx) ans = min(ans, bit[x]), x += x&-x; return ans; } int main() { int T, n; scanf("%d", &T); while(T--) { scanf("%d", &n); mx = 0; for (int i = 1; i <= n; i++) scanf("%d%d", &a[i].fi, &a[i].se), a[i].fi++, a[i].se++, mx = max(mx, a[i].se); //sort(a+1, a+1+n); mem(b, INF); mem(bit, INF); for (int i = 1; i <= n; i++) b[a[i].fi] = min(b[a[i].fi], a[i].se); for (int i = 1; i < mx; i ++) { if(b[i] != INF) add(i, b[i]); //cout << i << " " << b[i] << endl; } int st = 1, ans = 0; while(st <= mx) { st = query(st); if(st == INF) break; else ans++; } printf("%d ", ans); } return 0; }
39 完全背包
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long #define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head const int N = 555, M = 1e4 + 10; const int INF = 0x3f3f3f3f; pii a[N]; int dp[M]; int main() { int T, n, e, f, w; scanf("%d", &T); while(T--) { scanf("%d%d", &e, &f); scanf("%d", &n); for (int i = 1; i <= n; i++)scanf("%d%d", &a[i].fi, &a[i].se); mem(dp, INF); dp[0] = 0; w = f - e; for (int i = 1; i <= n; i++) { for (int j = a[i].se; j <= w; j++) { dp[j] = min(dp[j], dp[j-a[i].se]+a[i].fi); } } if(dp[w] == INF) printf("This is impossible. "); else printf("The minimum amount of money in the piggy-bank is %d. ", dp[w]); } return 0; }
3273 离散化+树状数组+二分
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long #define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head const int N = 2e5 + 5; pair<int, char> Q[N]; int a[N], bit[N], cnt[N], q; char s[10]; void add(int x, int a) { while(x <= q) bit[x] += a, x += x&-x; } int query(int x) { int ans = 0; while(x) ans += bit[x], x -= x&-x; return ans; } int MP[N]; int main() { int t; scanf("%d", &q); for (int i = 1; i <= q; i++) { scanf("%s%d", s, &t); Q[i] = mp(t, s[0]); a[i] = t; } sort(a+1, a+1+q); for (int i = 1; i <= q; i++) { t = lower_bound(a+1, a+1+q, Q[i].fi) - a; if(Q[i].se != 'K') { MP[t] = Q[i].fi; Q[i].fi = t; } } for (int i = 1; i <= q; i++) { if(Q[i].se == 'I') { if(!cnt[Q[i].fi])add(Q[i].fi, 1), cnt[Q[i].fi]++; } else if(Q[i].se == 'D') { if(cnt[Q[i].fi]) cnt[Q[i].fi]--, add(Q[i].fi, -1); } else if(Q[i].se == 'K') { if(Q[i].fi > query(q)) { printf("invalid "); continue; } int l = 1, r = q, m = (l+r) >> 1; while(l < r) { if(query(m) < Q[i].fi) l = m+1; else r = m; m = (l+r) >> 1; } printf("%d ", MP[m]); } else if(Q[i].se == 'C') { printf("%d ", query(Q[i].fi-1)); } } return 0; }
5449 stack
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long #define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head const int N = 2e3 + 5; char s[N]; int main() { int cs = 0; while(~scanf("%s", s+1)) { if(s[1] == '-') break; int n = strlen(s+1); int l = 0, ans = 0; for (int i = 1; i <= n; i++) { if(s[i] == '{') l++; else { if(l) l--; else ans++, l++; } } ans += l/2; printf("%d. %d ", ++cs, ans); } return 0; }
12471 dp+记忆化搜索
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long #define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head const int N = 2e3 + 5; int dp[N][N][3]; int dir[3][2] = {3, 2, -5, -10, -20, 5}; int dfs(int a, int b, int t) { if(a <= 0 || b <= 0) return -1; if(~dp[a][b][t]) return dp[a][b][t]; for (int i = 0; i < 3; i++) { if(i != t)dp[a][b][t] = max(dp[a][b][t], dfs(a+dir[i][0], b+dir[i][1], i)+1); } return dp[a][b][t]; } int main() { int T, h, a; mem(dp, -1); scanf("%d", &T); while(T--) { scanf("%d%d", &h, &a); printf("%d ", max(max(dfs(h, a, 0), dfs(h, a, 1)), dfs(h, a, 0))); } return 0; }
24 java大数
import java.math.*; import java.util.*; public class Main { public static void main(String[] args) { Scanner reader = new Scanner(System.in); int t; long n; t = reader.nextInt(); for (int i = 1; i <= t; i++) { n = reader.nextLong(); BigInteger ans = new BigInteger("1"); for (long j = 1; j <= n; j++) { ans = ans.multiply(BigInteger.valueOf(j)); } System.out.println(ans); } } }
9921 bfs水题
#include<bits/stdc++.h> using namespace std; #define fi first #define se second #define pi acos(-1.0) #define LL long long #define mp make_pair #define pb push_back #define ls rt<<1, l, m #define rs rt<<1|1, m+1, r #define ULL unsigned LL #define pll pair<LL, LL> #define pii pair<int, int> #define piii pair<int,pii> #define mem(a, b) memset(a, b, sizeof(a)) #define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); #define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout); //head const int N = 55; char s[N][N]; bool vis[N][N]; int n, m; int dir[8][2] = {1, 0, 0, 1, -1, 0, 0, -1, 1, -1, -1, 1, 1, 1, -1, -1}; queue<piii>q; int main() { int cs = 0; while(~scanf("%d%d", &n, &m)) { if(!n && !m) break; for (int i = 1; i <= n; i++) scanf("%s", s[i]+1); mem(vis, false); for (int i = 1; i <= n; i++) { for (int j = 1; j <= m; j++) { if(s[i][j] == 'A') { q.push({1, {i, j}}); vis[i][j] = true; } } } int ans = 0; while(!q.empty()) { piii p = q.front(); q.pop(); ans = p.fi; for (int i = 0; i < 8; i++) { int x = p.se.fi + dir[i][0]; int y = p.se.se + dir[i][1]; if(1 <= x && x <= n && 1 <= y && y <= m && !vis[x][y] && s[x][y] == s[p.se.fi][p.se.se]+1) { vis[x][y] = true; ans = p.fi + 1; q.push({p.fi+1, {x, y}}); } } } printf("Case %d: %d ", ++cs, ans); } return 0; }
总结1：按点赞数降序第一页都是水题，不过复习了之前学过的算法（线段树合并、区间dp之类的），学会了各种离线操作，所以不打算刷简单题了。