HDU 1836 畅通工程

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <cmath>
 5 #include <algorithm>
 6 #include <climits>
 7 #include <vector>
 8 #include <queue>
 9 #include <cstdlib>
10 #include <string>
11 #include <set>
12 #include <stack>
13 #define LL long long
14 #define pii pair<int,int>
15 #define INF 0x3f3f3f3f
16 using namespace std;
17 int mp[110][110],m,n,d[110];
18 priority_queue< pii,vector< pii >,greater< pii > >q;
19 bool done[110];
20 void prim(){
21     while(!q.empty()) q.pop();
22     for(int i = 1; i <= n; i++){
23         d[i] = mp[1][i];
24         done[i] = false;
25         q.push(make_pair(d[i],i));
26     }
27     bool flag = true;
28     int ans = 0;
29     done[1] = true;
30     while(!q.empty()){
31         int u = q.top().second;
32         int w = q.top().first;
33         q.pop();
34         if(done[u]) continue;
35         done[u] = true;
36         if(w >= INF){flag = false;break;}
37         ans += w;
38         for(int i = 1; i <= n; i++){
39             if(d[i] > mp[u][i]){
40                 d[i] = mp[u][i];
41                 q.push(make_pair(d[i],i));
42             }
43         }
44     }
45     if(flag) printf("%d\n",ans);
46     else puts("?");
47 }
48 int main() {
49     int i,j,u,v,w;
50     while(scanf("%d",&m),m){
51         scanf("%d",&n);
52         for(i = 0; i <= n; i++){
53             for(j = 0; j <= n; j++)
54                 mp[i][j] = INF;
55         }
56         for(i = 0; i < m; i++){
57             scanf("%d %d %d",&u,&v,&w);
58             mp[u][v] = mp[v][u] = w;
59         }
60         prim();
61     }
62     return 0;
63 }