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    =    50000        +    10;
const int A    =    20        +    1;

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 = 0;

    if (deep[a] < deep[b]) swap(a, b);
    for (int i = 0, delta = deep[a] - deep[b]; delta; delta >>= 1, ++i)
        if (delta & 1) ret += g[a][i], a = f[a][i];

    if (a == b) return ret;

    dec(i, 19, 0) 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][0];
    ret += g[b][0];

    return ret;
}

int main(){

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

        et = 0;
        memset(father, 0, sizeof father);
        memset(H, 0, sizeof H);


        rep(i, 1, m){
            scanf("%d%d%d", &x, &y, &z);Eddedge(x, y, z);
            int fa = getfather(x), fb = getfather(y);
            father[fa] = fb;
        }

        int l = 0, r = 0, now = 0;
        memset(List, 0, sizeof List);
        memset(deep, 0, sizeof deep);
        memset(v, false , sizeof v);
        memset(f, 0, sizeof f);
        memset(g, 0, sizeof g);

        rep(p, 1, n) if (!v[p]){
            for (l = 1, r = 1, v[p] = true, List[1] = p; l <= r; ++l){
                now = List[l];
                for_edge(i, now) if (!v[E[i]]){
                    v[E[i]] = true;
                    f[E[i]][0] = now;
                    g[E[i]][0] = V[i];
                    deep[E[i]] = deep[now] + 1;

                    for (int j = 0; f[E[i]][j]; ++j)
                        f[E[i]][j + 1] = f[f[E[i]][j]][j],
                            g[E[i]][j + 1] = 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
", Calc(x, y));
        }

    }

    return 0;

}