poj 2485 求最小生成树中 最长的一条边

Sample Input

1 //T

3 //n
0 990 692 //邻接矩阵
990 0 179
692 179 0
Sample Output

692

prim

# include <iostream>
# include <cstdio>
# include <cstring>
# include <algorithm>
# include <cmath>
# define LL long long
using namespace std ;

const int INF=0x3f3f3f3f;
const int MAXN=510;
bool vis[MAXN];
int lowc[MAXN];
int n ;
int cost[MAXN][MAXN] ;
int MAX = 0 ;

int Prim()//点是0~n-1
{
    int ans=0;
    memset(vis,false,sizeof(vis));
    vis[0]=true;
    for(int i=1;i<n;i++)lowc[i]=cost[0][i];
    for(int i=1;i<n;i++)
    {
        int minc=INF;
        int p=-1;
        for(int j=0;j<n;j++)
            if(!vis[j]&&minc>lowc[j])
            {
                minc=lowc[j];
                p=j;
            }
            if(minc==INF)return -1;//原图不连通
            ans+=minc;
            if (minc > MAX)
                MAX = minc ;
            vis[p]=true;
            for(int j=0;j<n;j++)
                if(!vis[j]&&lowc[j]>cost[p][j])
                    lowc[j]=cost[p][j];
    }
    return ans;
}

int main()
{

   // freopen("in.txt","r",stdin) ;
    int T ;
    cin>>T ;
    while(T--)
    {
        cin>>n ;
        int w ;
        int i , j ;
        for (i = 0 ; i < n ; i++)
            for (j = 0 ; j < n ; j++)
               {
                   cin>>w ;
                   if(w==0)
                     cost[i][j] = INF ;
                   else
                     cost[i][j] = w ;
               }
        MAX = 0 ;
        Prim() ;
        cout<<MAX<<endl ;

    }
    return 0 ;
}