学了一早上倍增，感觉lca还是tarjan好写。
poj1330
1 #include <stdio.h> 2 #include <string.h> 3 #include <queue> 4 #include <algorithm> 5 #define DEG 20//2^20 6 #define maxn 10010 7 using namespace std; 8 struct node 9 { 10 int v, next; 11 }a[maxn*2]; 12 int q[4*maxn], fa[maxn][DEG], root, n, m, u, v, tot, first[maxn*2], dis[maxn]; 13 bool flag[maxn]; 14 void addedge(int st, int end) 15 { 16 a[tot].v = end; 17 a[tot].next = first[st]; first[st] = tot++; 18 } 19 void init() 20 { 21 tot = 0; 22 memset(first, -1, sizeof(first)); 23 memset(flag, 0, sizeof(flag)); 24 } 25 void bfs(int root) 26 { 27 queue<int >que; 28 dis[root] = 0; 29 fa[root][0] = root;//root's 2^0 father is root 30 que.push(root); 31 //q[0] = root; 32 //int head = 0,tail = 1; 33 while (!que.empty()) 34 { 35 //int u = q[head++]; 36 int u = que.front();que.pop(); 37 for (int i = 1; i < DEG; i++)/*the father from 2^1 ~ 2^DEG*/fa[u][i] = fa[fa[u][i-1]][i-1];//u's 2^i father is u's (2^(i-1))^(i-1) 38 for (int e = first[u]; e != -1; e = a[e].next) 39 { 40 int v = a[e].v; 41 if (v == fa[u][0])continue;//if u's father is v,continue, it can't vis his fahter 42 dis[v] = dis[u] + 1; 43 fa[v][0] = u; 44 //q[++tail] = v; 45 que.push(v); 46 } 47 } 48 } 49 int LCA(int u, int v) 50 { 51 if (dis[u] > dis[v])swap(u, v); 52 int du = dis[u], dv = dis[v]; 53 int tu = u, tv = v; 54 for (int det = dv - du, i = 0;det; det>>=1, i++) 55 if (det&1)//det if u's high - v's high; 56 tv = fa[tv][i];//let deeper point up(2^i) until det = 1; 57 if (tu == tv)return tu; 58 for (int i = DEG - 1; i >= 0; i--) 59 { 60 if (fa[tu][i] == fa[tv][i])continue; 61 tu = fa[tu][i]; 62 tv = fa[tv][i]; 63 } 64 return fa[tu][0]; 65 } 66 int main() 67 { 68 int T; 69 scanf("%d", &T); 70 while (T--) 71 { 72 scanf("%d", &n); 73 init(); 74 for (int i = 1; i < n; i++) 75 { 76 scanf("%d %d", &u, &v); 77 addedge(u, v);addedge(v, u); 78 flag[v] = 1; 79 } 80 int root; 81 for (int i = 1; i <= n; i++) 82 { 83 if (!flag[i]) 84 { 85 root = i;break; 86 } 87 } 88 bfs(root);//dfs(root); 89 scanf("%d %d", &u, &v); 90 printf("%d ", LCA(u,v)); 91 } 92 }
bzoj3732
1 /************************************************************** 2 Problem: 3732 3 User: z52527 4 Language: C++ 5 Result: Accepted 6 Time:392 ms 7 Memory:7304 kb 8 ****************************************************************/ 9 10 #include <stdio.h> 11 #include <string.h> 12 #include <algorithm> 13 #define DEG 20//2^20 14 #define maxn 30010 15 using namespace std; 16 struct node 17 { 18 int u, v, w, next; 19 }a[maxn], b[maxn]; 20 int first[maxn], m, n, q, tot; 21 int dis[maxn], fa[maxn][DEG], maxf[maxn][DEG], ans, father[maxn]; 22 void addedge(int st, int end, int val) 23 { 24 b[++tot].u = st;b[tot].v = end;b[tot].w = val; 25 b[tot].next = first[st]; first[st] = tot; 26 } 27 int getfather(int x){return father[x] == x ? x : getfather(father[x]);} 28 int cmp (node a, node b){return a.w < b.w;} 29 int dfs(int u) 30 { 31 dis[u] = dis[fa[u][0]]+1; 32 for (int e = first[u]; e != -1; e = b[e].next) 33 { 34 if (b[e].v == fa[u][0]) continue; 35 fa[b[e].v][0] = u; 36 maxf[b[e].v][0] = b[e].w; 37 dfs(b[e].v); 38 } 39 } 40 int lca(int u, int v) 41 { 42 ans = 0; 43 if (dis[u] > dis[v])swap(u, v); 44 int du = dis[u], dv = dis[v]; 45 int fu = u, fv = v; 46 for (int def = dv - du, i = 0; def; def>>=1, i++) 47 if (def&1) 48 ans = max(ans, maxf[fv][i]), fv = fa[fv][i]; 49 if (fu == fv)return ans; 50 for (int i = 14; i >=0; i--) 51 { 52 if (fa[fu][i] == fa[fv][i])continue; 53 ans = max(maxf[fu][i], ans); 54 ans = max(maxf[fv][i], ans); 55 fu = fa[fu][i]; 56 fv = fa[fv][i]; 57 } 58 ans = max(maxf[fu][0], ans); 59 ans = max(maxf[fv][0], ans); 60 return ans; 61 } 62 int main() 63 { 64 int u, v, w; 65 scanf("%d %d %d", &n, &m, &q); 66 for (int i = 1; i <= n; i++)father[i] = i; 67 memset(first, -1, sizeof(first)); 68 for (int i = 1; i <= m; i++) 69 { 70 scanf("%d %d %d", &u, &v, &w); 71 a[i].u = u;a[i].v = v;a[i].w = w; 72 } 73 sort(a+1, a+1+m, cmp); 74 for (int i = 1; i <= m; i++) 75 { 76 u = getfather(a[i].u); 77 v = getfather(a[i].v); 78 if (u != v) 79 { 80 father[u] = v; 81 addedge(a[i].u, a[i].v, a[i].w); 82 addedge(a[i].v, a[i].u, a[i].w); 83 } 84 } 85 dfs(1); 86 //scanf("%d", &q); 87 for(int j = 1;j <= 14; j++) 88 for(int i = 1;i <= n; i++) 89 fa[i][j] = fa[ fa[i][j-1] ][j-1],maxf[i][j]=max( maxf[i][j-1] , maxf[ fa[i][j-1] ][j-1] ); 90 for (int i = 1; i <= q; i++) 91 { 92 scanf("%d %d", &u, &v); 93 printf("%d ", lca(u, v)); 94 } 95 }
noip2013 货车运输
1 #include <stdio.h> 2 #include <string.h> 3 #include <algorithm> 4 #define DEG 20//2^20 5 #define maxn 50010 6 using namespace std; 7 struct node 8 { 9 int u, v, w, next; 10 }a[maxn], b[maxn]; 11 int first[maxn], m, n, q, tot; 12 int dis[maxn], fa[maxn][DEG], maxf[maxn][DEG], ans, father[maxn]; 13 void addedge(int st, int end, int val) 14 { 15 b[++tot].u = st;b[tot].v = end;b[tot].w = val; 16 b[tot].next = first[st]; first[st] = tot; 17 } 18 int getfather(int x){return father[x] == x ? x : getfather(father[x]);} 19 int cmp (node a, node b){return a.w > b.w;} 20 int dfs(int u) 21 { 22 dis[u] = dis[fa[u][0]]+1; 23 for (int e = first[u]; e != -1; e = b[e].next) 24 { 25 if (b[e].v == fa[u][0]) continue; 26 fa[b[e].v][0] = u; 27 maxf[b[e].v][0] = b[e].w; 28 dfs(b[e].v); 29 } 30 } 31 int lca(int u, int v) 32 { 33 ans = 2000000000; 34 if (dis[u] > dis[v])swap(u, v); 35 int du = dis[u], dv = dis[v]; 36 int fu = u, fv = v; 37 for (int def = dv - du, i = 0; def; def>>=1, i++) 38 if (def&1) 39 ans = min(ans, maxf[fv][i]), fv = fa[fv][i]; 40 if (fu == fv)return ans; 41 for (int i = 16; i >= 0; i--) 42 { 43 if (fa[fu][i] == fa[fv][i])continue; 44 ans = min(maxf[fu][i], ans); 45 ans = min(maxf[fv][i], ans); 46 fu = fa[fu][i]; 47 fv = fa[fv][i]; 48 } 49 ans = min(maxf[fu][0], ans); 50 ans = min(maxf[fv][0], ans); 51 return ans; 52 } 53 int main() 54 { 55 int u, v, w; 56 scanf("%d %d", &n, &m); 57 for (int i = 1; i <= n; i++)father[i] = i; 58 memset(first, -1, sizeof(first)); 59 for (int i = 1; i <= m; i++) 60 { 61 scanf("%d %d %d", &u, &v, &w); 62 a[i].u = u;a[i].v = v;a[i].w = w; 63 } 64 sort(a+1, a+1+m, cmp); 65 for (int i = 1; i <= m; i++) 66 { 67 u = getfather(a[i].u); 68 v = getfather(a[i].v); 69 if (u != v) 70 { 71 father[u] = v; 72 addedge(a[i].u, a[i].v, a[i].w); 73 addedge(a[i].v, a[i].u, a[i].w); 74 } 75 } 76 dfs(1); 77 scanf("%d", &q); 78 for(int j = 1;j <= 16; j++) 79 for(int i = 1;i <= n; i++) 80 fa[i][j] = fa[ fa[i][j-1] ][j-1],maxf[i][j]=min( maxf[i][j-1] , maxf[ fa[i][j-1] ][j-1] ); 81 for (int i = 1; i <= q; i++) 82 { 83 scanf("%d %d", &u, &v); 84 if (getfather(u) != getfather(v)){printf("-1 ");continue;} 85 printf("%d ", lca(u, v)); 86 } 87 }