HDU 2874 Connections between cities（LCA）

题目链接 Connections between cities

LCA的模板题啦。

 #include <bits/stdc++.h>

 using namespace std;

 #define REP(i,n)        for(int i(0); i <  (n); ++i)
 #define rep(i,a,b)        for(int i(a); i <= (b); ++i)
 #define dec(i,a,b)        for(int i(a); i >= (b); --i)
 #define for_edge(i,x)        for(int i = H[x]; i; i = X[i])

 const int N    =            +    ;
 const int A    =            +    ;

 int father[N], List[N], deep[N], E[N], X[N], H[N], V[N];
 int f[N][A], g[N][A];
 bool v[N];
 int n, m, q, x, y, z;
 int et;

 inline void Eddedge(int a, int b, int c){
     E[++et] = b, X[et] = H[a], H[a] = et, V[et] = c;
     E[++et] = a, X[et] = H[b], H[b] = et, V[et] = c;
 }

 int getfather(int x){ return father[x] ? father[x]  = getfather(father[x]) : x; } 

 int Calc(int a, int b){
     int ret = ;

     if (deep[a] < deep[b]) swap(a, b);
     for (int i = , delta = deep[a] - deep[b]; delta; delta >>= , ++i)
         if (delta & ) ret += g[a][i], a = f[a][i];

     if (a == b) return ret;

     dec(i, , ) if (f[a][i] != f[b][i]){
         ret += g[a][i];
         ret += g[b][i];
         a = f[a][i];
         b = f[b][i];
     }

     ret += g[a][];
     ret += g[b][];

     return ret;
 }

 int main(){

     while (~scanf("%d%d%d", &n, &m, &q)){

         et = ;
         memset(father, , sizeof father);
         memset(H, , sizeof H);

         rep(i, , m){
             scanf("%d%d%d", &x, &y, &z);Eddedge(x, y, z);
             int fa = getfather(x), fb = getfather(y);
             father[fa] = fb;
         }

         int l = , r = , now = ;
         memset(List, , sizeof List);
         memset(deep, , sizeof deep);
         memset(v, false , sizeof v);
         memset(f, , sizeof f);
         memset(g, , sizeof g);

         rep(p, , n) if (!v[p]){
             for (l = , r = , v[p] = true, List[] = p; l <= r; ++l){
                 now = List[l];
                 for_edge(i, now) if (!v[E[i]]){
                     v[E[i]] = true;
                     f[E[i]][] = now;
                     g[E[i]][] = V[i];
                     deep[E[i]] = deep[now] + ;

                     for (int j = ; f[E[i]][j]; ++j)
                         f[E[i]][j + ] = f[f[E[i]][j]][j],
                             g[E[i]][j + ] = g[E[i]][j] + g[f[E[i]][j]][j];

                     List[++r] = E[i];
                 }
             }
         }

         while (q--){
             scanf("%d%d", &x, &y);
             int fa = getfather(x), fb = getfather(y);
             if (fa != fb) puts("Not connected"); else printf("%d\n", Calc(x, y));
         }

     }

     return ;

 }