hdu-1863-畅通工程(kruskal算法模板)

 题目链接

 /*
     Name:hdu-1863-畅通工程
     Copyright:
     Author:
     Date: 2018/4/18 10:19:03
     Description:
     kruskal算法
 */
 #include <iostream>
 #include <cstring>
 #include <algorithm>
 #include <cstdio>
 using namespace std;
 const int MAXN = ;
 struct edge{
     int x, y, w;
     edge(int x=,int y=, int w=):x(x),y(y),w(w){
     };
 } e[];
 int N ,M, cnt;
 int fa[MAXN];
 int getfather(int x) {//查找
     if (x == fa[x]) return x;
     else return fa[x] = getfather(fa[x]);
 }
 bool cmp(edge a, edge b)  {//从小到大排序
     return a.w < b.w;
 }
 int kruskal() {
     sort(e+, e+M+, cmp);
     cnt = M;//边数
     int ans = ;
     for (int i=; i<=N; ++i) fa[i] = i;
     for (int i=; i<=M; ++i) {
         int t1 = getfather(e[i].x);
         int t2 = getfather(e[i].y);
         if (t1 != t2) {
             fa[t1] = t2;
             ans += e[i].w;
             cnt--;//加入结点
             if (cnt == ) break;////// 加入n-1条边说明已经生成最小生成树
         }
     }
     return ans;
 }
 int main()
 {
 //    freopen("in.txt", "r", stdin);
     while (cin>>N>>M, N) {
         memset(e, , sizeof(e));
         memset(fa, , sizeof(fa));
         for (int i=; i<=N; i++) {
             scanf("%d %d %d", &e[i].x, &e[i].y, &e[i].w);
         }
         int ans = kruskal();
         if (cnt != ) cout<<"?"<<endl;
         else cout<<ans<<endl;
     }
     return ;
 }