Codeforces Edu Round 82 (Rated for Div. 2)

题目链接：https://codeforces.com/contest/1303

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A：

白给

/* basic header */
#include <bits/stdc++.h>
/* define */
#define ll long long
#define dou double
#define pb emplace_back
#define mp make_pair
#define sot(a,b) sort(a+1,a+1+b)
#define rep1(i,a,b) for(int i=a;i<=b;++i)
#define rep0(i,a,b) for(int i=a;i<b;++i)
#define eps 1e-8
#define int_inf 0x3f3f3f3f
#define ll_inf 0x7f7f7f7f7f7f7f7f
#define lson (curpos<<1)
#define rson (curpos<<1|1)
/* namespace */
using namespace std;
/* header end */

const int maxn = 110;
int t;
char s[maxn];

int main() {
    scanf("%d", &t);
    while (t--) {
        int ans = 0;
        scanf("%s", s + 1);
        int len = strlen(s + 1);
        int p, q;
        for (p = 1; p <= len; p++)
            if (s[p] == '1') break;
        for (q = len; q >= 1; q--)
            if (s[q] == '1') break;
        for (int i = p; i <= q; i++)
            if (s[i] == '0') ans++;
        printf("%d
", ans);
    }
    return 0;
}

B：

写了个傻逼做法，崩了

// /* basic header */
// #include <bits/stdc++.h>
// /* define */
// #define ll long long
// #define dou double
// #define pb emplace_back
// #define mp make_pair
// #define sot(a,b) sort(a+1,a+1+b)
// #define rep1(i,a,b) for(int i=a;i<=b;++i)
// #define rep0(i,a,b) for(int i=a;i<b;++i)
// #define eps 1e-8
// #define int_inf 0x3f3f3f3f
// #define ll_inf 0x7f7f7f7f7f7f7f7f
// #define lson (curpos<<1)
// #define rson (curpos<<1|1)
// /* namespace */
// using namespace std;
// /* header end */

// int t;
// ll n, g, b;

// int main() {
//     scanf("%d", &t);
//     while (t--) {
//         scanf("%lld%lld%lld", &n, &g, &b);
//         ll goodNum = 0, badNum = 0, weekCount, ans = 0;
//         goodNum = n & 1 ? n / 2 + 1 : n / 2; badNum = n - goodNum;
//         weekCount = goodNum / g - 1;
//         goodNum -= weekCount * g, badNum -= weekCount * b;
//         if (goodNum < 0) goodNum = 0;
//         if (badNum < 0) badNum = 0;
//         ans = weekCount * (g + b);
//         while (goodNum) {
//             int delta = min(g, goodNum);
//             ans += delta; goodNum -= delta;
//             if (goodNum <= 0) break;
//             badNum -= b;
//             if (badNum < 0) badNum = 0;
//             ans += b;
//         }
//         ans += badNum;
//         printf("%lld
", ans);
//     }
//     return 0;
// }

/* basic header */
#include <bits/stdc++.h>
/* define */
#define ll long long
#define dou double
#define pb emplace_back
#define mp make_pair
#define sot(a,b) sort(a+1,a+1+b)
#define rep1(i,a,b) for(int i=a;i<=b;++i)
#define rep0(i,a,b) for(int i=a;i<b;++i)
#define eps 1e-8
#define int_inf 0x3f3f3f3f
#define ll_inf 0x7f7f7f7f7f7f7f7f
#define lson (curpos<<1)
#define rson (curpos<<1|1)
/* namespace */
using namespace std;
/* header end */

int t;

int main() {
    cin >> t;
    while (t--) {
        ll N, n, g, b; cin >> n >> g >> b;
        N = n, n = n + 1 >> 1;
        ll ans = (n / g) * (g + b) + n % g;
        if (n % g == 0 && n / g) ans -= b;
        cout << max(ans, N) << endl;
    }
    return 0;
}

C：

建无向图dfs即可

/* basic header */
#include <bits/stdc++.h>
/* define */
#define ll long long
#define dou double
#define pb emplace_back
#define mp make_pair
#define sot(a,b) sort(a+1,a+1+b)
#define rep1(i,a,b) for(int i=a;i<=b;++i)
#define rep0(i,a,b) for(int i=a;i<b;++i)
#define eps 1e-8
#define int_inf 0x3f3f3f3f
#define ll_inf 0x7f7f7f7f7f7f7f7f
#define lson (curpos<<1)
#define rson (curpos<<1|1)
/* namespace */
using namespace std;
/* header end */

int t;
vector<int>edge[26];
string s, ans;
bool used[26];

void dfs(int v) {
    if (used[v]) return;
    ans += char('a' + v);
    used[v] = 1;
    for (auto to : edge[v]) {
        if (!used[to]) dfs(to);
    }
}

int main() {
    cin >> t;
    while (t--) {
        ans = "";
        for (int i = 0; i < 26; i++) edge[i].clear();
        memset(used, 0, sizeof(used));
        cin >> s;
        int n = s.size();
        for (int i = 0; i < n - 1; i++) {
            int a = s[i] - 'a', b = s[i + 1] - 'a';
            edge[a].pb(b), edge[b].pb(a);
        }
        for (int i = 0; i < 26; i++) {
            sort(edge[i].begin(), edge[i].end());
            edge[i].erase(unique(edge[i].begin(), edge[i].end()), edge[i].end());
        }
        for (int i = 0; i < 26; i++)
            if (!used[i] && edge[i].size() <= 1) dfs(i);
        if (ans.size() < 26) {
            puts("NO");
            continue;
        }
        int flag = 1;
        for (int i = 0; i < n - 1; i++) {
            int pos1, pos2;
            for (int j = 0; j < ans.size(); j++) {
                if (ans[j] == s[i]) pos1 = j;
                if (ans[j] == s[i + 1]) pos2 = j;
            }
            if (abs(pos1 - pos2) != 1) flag = 0;
        }
        if (!flag) puts("NO");
        else printf("YES
%s
", ans.c_str());
    }
}

D：

枚举2的幂，判断能否从低到高凑出n

/* basic header */
#include <bits/stdc++.h>
/* define */
#define ll long long
#define dou double
#define pb emplace_back
#define mp make_pair
#define sot(a,b) sort(a+1,a+1+b)
#define rep1(i,a,b) for(int i=a;i<=b;++i)
#define rep0(i,a,b) for(int i=a;i<b;++i)
#define eps 1e-8
#define int_inf 0x3f3f3f3f
#define ll_inf 0x7f7f7f7f7f7f7f7f
#define lson (curpos<<1)
#define rson (curpos<<1|1)
/* namespace */
using namespace std;
/* header end */

ll n, sum;
int t, m, ans;
map<ll, int>cnt;

int main() {
    scanf("%d", &t);
    while (t--) {
        cnt.clear();
        sum = 0, ans = 0;
        scanf("%lld%d", &n, &m);
        for (int i = 0; i < m; i++) {
            ll x; scanf("%lld", &x);
            sum += x; cnt[x]++;
        }
        if (sum < n) {
            puts("-1");
            continue;
        }
        for (int i = 0; i < 63; i++) {
            ll j = 1ll << i;
            if (cnt[j] < ((n >> i) & 1)) {
                ans++;
                cnt[j] += 2;
                cnt[j << 1] -= 1;
            }
            cnt[j << 1] += (cnt[j] - ((n >> i) & 1)) / 2;
        }
        printf("%d
", ans);
    }
    return 0;
}