HDU 1879 继续畅通工程

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http://acm.hdu.edu.cn/showproblem.php?pid=1879

克鲁斯卡尔算法求解最小生成树（MST）

#include <stdio.h>#include <string.h>#include <iostream>#include <algorithm>using namespace std;int father[110],n,m;struct node{    int from,to,cost;}edge[5010];void Init(){    for(int i=1; i<=n; i++)        father[i] = i;}int Find(int x){    if(x == father[x])  return x;    return Find(father[x]);}void Union(int fx, int fy){    father[fy] = fx;}bool cmp(const node &A, const node &B){    return A.cost < B.cost;}int main(){//    freopen("in.txt", "r", stdin);    while(scanf("%d",&n) == 1 && n){        Init();        m = n*(n-1)/2;        int from,to,cost,key;        for(int i=0; i<m; i++){            scanf("%d%d%d%d",&from,&to,&cost,&key);            edge[i].from = from,edge[i].to = to;            if(key) edge[i].cost = 0;            else    edge[i].cost = cost;        }        sort(edge, edge+m, cmp);///将边按照权值大小排序        int cnt = n, ans = 0;        for(int i=0; i<m && cnt > 1; i++){///cnt = 1代表已经找到一棵最小生成树            int fx = Find(edge[i].from), fy = Find(edge[i].to);            if(fx != fy){                Union(fx, fy);                cnt--;                ans += edge[i].cost;            }        }        printf("%d\n",ans);    }    return 0;}

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