POJ 2485

 #include<iostream>
 #define MAXN 505
 #define inf 1000000000
 using namespace std;
 typedef int elem_t;
 int _m[MAXN][MAXN];
 int pre[MAXN];
 elem_t prim(int n,elem_t mat[][MAXN],int* pre);
 int main()
 {
     //freopen("acm.acm","r",stdin);
     int num;
     int i;
     int j;
     int min = inf;
     int time;
     scanf("%d",&time);
     while(time --)
     {
         scanf("%d",&num);
         min = ;
         for(i = ; i < num; ++ i)
         {
             for(j = ; j < num; ++ j)
                 _m[i][j] = inf;
         }
         for(i = ; i < num; ++ i)
         {
             for(j = ; j < num; ++ j)
             {
                 scanf("%d",&_m[i][j]);
             }
         }
         prim(num,_m,pre);
         for(i  = num-; i >= ; -- i)
         {
             j = i;
             while(pre[j] != -)
             {
                 if(_m[pre[j]][j] > min)
                     min = _m[pre[j]][j];
                 j = pre[j];
             }
         }
         cout<<min<<endl;
     }
 }

 ////////////////////////////////////////////////

 elem_t prim(int n,elem_t mat[][MAXN],int* pre){
     elem_t min[MAXN],ret=;
     int v[MAXN],i,j,k;
     for (i=;i<n;i++)
         min[i]=inf,v[i]=,pre[i]=-;
     for (min[j=]=;j<n;j++){
         for (k=-,i=;i<n;i++)
             if (!v[i]&&(k==-||min[i]<min[k]))
                 k=i;
         for (v[k]=,ret+=min[k],i=;i<n;i++)
             if (!v[i]&&mat[k][i]<min[i])
                 min[i]=mat[pre[i]=k][i];
     }
     return ret;
 }