ZOJ 2966 Build The Electric System【最小生成树】

//2632030 2011-08-18 16:57:56 Accepted 2966 C++ 0 1652 ylwh@Unknown#include <stdio.h>#include <string.h>#include <stdlib.h>#include <math.h>#include <algorithm>using namespace std;#define N 501struct edge{int x, y, cost;}e[N * N / 2];int root[N];int find_root(int x){int temp = x;while(temp != root[temp])temp = root[temp];root[x] = temp;return temp;}int cmp(struct edge a, struct edge b){return a.cost < b.cost;}int main(){int t, n, E, i, j, a, b, x, y, cnt, ans;scanf("%d", &t);while(t--){cnt = -1;ans = 0;scanf("%d%d", &n, &E);for(i=0; i<n; i++)root[i] = i;for(i=0; i<E; i++){scanf("%d%d%d", &x, &y, &j);if(j){e[++cnt].x = x;e[  cnt].y = y;e[  cnt].cost = j;}else{a = find_root(x);b = find_root(y);if(a > b)root[a] = b;else if(a < b)root[b] = a;}}sort(e, e + cnt + 1, cmp);for(i=0; i<=cnt; i++){a = find_root(e[i].x);b = find_root(e[i].y);if(a != b){ans += e[i].cost;if(a > b)root[a] = b;elseroot[b] = a;}}printf("%d\n", ans);}    return 0;}