HDU 2874 Connections between cities（LCA）
题目链接 Connections between cities
LCA的模板题啦。
1 #include <bits/stdc++.h> 2 3 using namespace std; 4 5 #define REP(i,n) for(int i(0); i < (n); ++i) 6 #define rep(i,a,b) for(int i(a); i <= (b); ++i) 7 #define dec(i,a,b) for(int i(a); i >= (b); --i) 8 #define for_edge(i,x) for(int i = H[x]; i; i = X[i]) 9 10 const int N = 50000 + 10; 11 const int A = 20 + 1; 12 13 int father[N], List[N], deep[N], E[N], X[N], H[N], V[N]; 14 int f[N][A], g[N][A]; 15 bool v[N]; 16 int n, m, q, x, y, z; 17 int et; 18 19 inline void Eddedge(int a, int b, int c){ 20 E[++et] = b, X[et] = H[a], H[a] = et, V[et] = c; 21 E[++et] = a, X[et] = H[b], H[b] = et, V[et] = c; 22 } 23 24 int getfather(int x){ return father[x] ? father[x] = getfather(father[x]) : x; } 25 26 int Calc(int a, int b){ 27 int ret = 0; 28 29 if (deep[a] < deep[b]) swap(a, b); 30 for (int i = 0, delta = deep[a] - deep[b]; delta; delta >>= 1, ++i) 31 if (delta & 1) ret += g[a][i], a = f[a][i]; 32 33 if (a == b) return ret; 34 35 dec(i, 19, 0) if (f[a][i] != f[b][i]){ 36 ret += g[a][i]; 37 ret += g[b][i]; 38 a = f[a][i]; 39 b = f[b][i]; 40 } 41 42 ret += g[a][0]; 43 ret += g[b][0]; 44 45 return ret; 46 } 47 48 int main(){ 49 50 while (~scanf("%d%d%d", &n, &m, &q)){ 51 52 et = 0; 53 memset(father, 0, sizeof father); 54 memset(H, 0, sizeof H); 55 56 57 rep(i, 1, m){ 58 scanf("%d%d%d", &x, &y, &z);Eddedge(x, y, z); 59 int fa = getfather(x), fb = getfather(y); 60 father[fa] = fb; 61 } 62 63 int l = 0, r = 0, now = 0; 64 memset(List, 0, sizeof List); 65 memset(deep, 0, sizeof deep); 66 memset(v, false , sizeof v); 67 memset(f, 0, sizeof f); 68 memset(g, 0, sizeof g); 69 70 rep(p, 1, n) if (!v[p]){ 71 for (l = 1, r = 1, v[p] = true, List[1] = p; l <= r; ++l){ 72 now = List[l]; 73 for_edge(i, now) if (!v[E[i]]){ 74 v[E[i]] = true; 75 f[E[i]][0] = now; 76 g[E[i]][0] = V[i]; 77 deep[E[i]] = deep[now] + 1; 78 79 for (int j = 0; f[E[i]][j]; ++j) 80 f[E[i]][j + 1] = f[f[E[i]][j]][j], 81 g[E[i]][j + 1] = g[E[i]][j] + g[f[E[i]][j]][j]; 82 83 List[++r] = E[i]; 84 } 85 } 86 } 87 88 while (q--){ 89 scanf("%d%d", &x, &y); 90 int fa = getfather(x), fb = getfather(y); 91 if (fa != fb) puts("Not connected"); else printf("%d\n", Calc(x, y)); 92 } 93 94 } 95 96 return 0; 97 98 }
