POJ-2485 Highways(最小生成树)

 1 #include <cstdio>
 2 #include <cmath>
 3 #include <cstring>
 4 #include <cstdlib>
 5 #include <queue>
 6 #include <stack>
 7 #include <vector>
 8 #include <iostream>
 9 #include "algorithm"
10 using namespace std;
11 typedef long long LL;
12 const int MAX=505;
13 int t;
14 int n,m;
15 int a[MAX][MAX];
16 struct Edge{
17     int u,v;
18     int w;
19 }edge[MAX*MAX];
20 int fa[MAX*MAX];
21 bool cmp(Edge x,Edge y){
22     return x.w<y.w;
23 }
24 void init(){
25     int i,j;
26     scanf("%d",&n);
27     for (i=1;i<=n;i++)
28      for (j=1;j<=n;j++)
29       scanf("%d",&a[i][j]);
30     m=0;
31     for (i=1;i<=n;i++)
32      for (j=i+1;j<=n;j++)
33      {edge[++m].u=i;
34       edge[m].v=j;
35       edge[m].w=a[i][j];
36      }
37     sort(edge+1,edge+m+1,cmp);
38 }
39 int getfather(int x){
40     if (fa[x]==x)
41      return x;
42     return fa[x]=getfather(fa[x]);
43 }
44 int main(){
45     freopen ("highways.in","r",stdin);
46     freopen ("highways.out","w",stdout);
47     int i,j;
48     int tx,ty;
49     scanf("%d",&t);
50     while (t--){
51     init();int ans=0;
52     for (i=1;i<=m;i++)
53      fa[i]=i;
54     for (i=1;i<=m;i++)
55     {tx=getfather(edge[i].u);
56      ty=getfather(edge[i].v);
57      if (tx!=ty)
58      {fa[tx]=ty;
59       ans=max(ans,edge[i].w);
60      }
61     }
62     printf("%d\n",ans);}
63     return 0;
64 }