POJ 2485 Highways

 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 const int maxn = 510;
18 struct arc {
19     int to,w;
20     arc(int x = 0,int y = 0):to(x),w(y) {}
21 };
22 vector<arc>g[maxn];
23 int n,d[maxn];
24 bool done[maxn];
25 priority_queue< pii,vector< pii >,greater< pii > >q;
26 int prim() {
27     while(!q.empty()) q.pop();
28     d[1] = 0;
29     q.push(make_pair(d[1],1));
30     int ans = 0;
31     while(!q.empty()){
32         int u = q.top().second;
33         int w = q.top().first;
34         q.pop();
35         if(done[u]) continue;
36         done[u] = true;
37         ans = max(w,ans);
38         for(int i = 0; i < g[u].size(); i++){
39             if(d[g[u][i].to] > g[u][i].w){
40                 d[g[u][i].to] = g[u][i].w;
41                 q.push(make_pair(d[g[u][i].to],g[u][i].to));
42             }
43         }
44     }
45     return ans;
46 }
47 int main() {
48     int t,i,j,w;
49     scanf("%d",&t);
50     while(t--) {
51         scanf("%d",&n);
52         for(i = 0; i <= n; i++) {
53             g[i].clear();
54             d[i] = INF;
55             done[i] = false;
56         }
57         for(i = 1; i <= n; i++) {
58             for(j = 1; j <= n; j++) {
59                 scanf("%d",&w);
60                 if(i != j) g[i].push_back(arc(j,w));
61             }
62         }
63         printf("%d\n",prim());
64     }
65     return 0;
66 }