题目链接
1 /*
2 Name:hdu-1863-畅通工程
3 Copyright:
4 Author:
5 Date: 2018/4/18 10:19:03
6 Description:
7 kruskal算法
8 */
9 #include <iostream>
10 #include <cstring>
11 #include <algorithm>
12 #include <cstdio>
13 using namespace std;
14 const int MAXN = 110;
15 struct edge{
16 int x, y, w;
17 edge(int x=0,int y=0, int w=0):x(x),y(y),w(w){
18 };
19 } e[5000];
20 int N ,M, cnt;
21 int fa[MAXN];
22 int getfather(int x) {//查找
23 if (x == fa[x]) return x;
24 else return fa[x] = getfather(fa[x]);
25 }
26 bool cmp(edge a, edge b) {//从小到大排序
27 return a.w < b.w;
28 }
29 int kruskal() {
30 sort(e+1, e+M+1, cmp);
31 cnt = M;//边数
32 int ans = 0;
33 for (int i=1; i<=N; ++i) fa[i] = i;
34 for (int i=1; i<=M; ++i) {
35 int t1 = getfather(e[i].x);
36 int t2 = getfather(e[i].y);
37 if (t1 != t2) {
38 fa[t1] = t2;
39 ans += e[i].w;
40 cnt--;//加入结点
41 if (cnt == 1) break;////// 加入n-1条边说明已经生成最小生成树
42 }
43 }
44 return ans;
45 }
46 int main()
47 {
48 // freopen("in.txt", "r", stdin);
49 while (cin>>N>>M, N) {
50 memset(e, 0, sizeof(e));
51 memset(fa, 0, sizeof(fa));
52 for (int i=1; i<=N; i++) {
53 scanf("%d %d %d", &e[i].x, &e[i].y, &e[i].w);
54 }
55 int ans = kruskal();
56 if (cnt != 1) cout<<"?"<<endl;
57 else cout<<ans<<endl;
58 }
59 return 0;
60 }
61
62
