Poj2377--Bad Cowtractors（最大生成树）

#include <cstdio>
#include <cstring>
#include <iostream>
using namespace std;
const int INF = 0x3f3f3f3f; 
int map[1010][1010], dis[1010], vis[1010];
int n, m;
void Prim()
{
    int TotalMon = 0;
    memset(vis, 0, sizeof(vis));
    for(int i = 1; i <= n; i++)
        dis[i] = map[1][i];
    vis[1] = 1; 
    for(int i = 1; i < n; i++){
        int temp = 1, max = 0;
        for(int j = 1; j <= n; j++)
        {
            if(!vis[j] && dis[j] > max)
            {
                temp = j;
                max = dis[j];    
            }    
        }
        if(max == 0){
            printf("-1\n");
            return;
        }
        TotalMon += max;
        vis[temp] = 1;
        for(int j = 1; j <= n; j++)
            if(!vis[j] && dis[j] < map[temp][j] && map[temp][j] != INF)
                dis[j] = map[temp][j];
            
    }    
    printf("%d\n", TotalMon);
} 
int main()
{
    while(~scanf("%d %d", &n, &m))
    {
        int u, v, w;
        memset(map, -1, sizeof(map));       //权值初始化为负；
        for(int i = 0; i < m; i++){
            scanf("%d %d %d", &u, &v, &w); 
            if(map[u][v] < w)
                map[u][v] = map[v][u] = w;
        }
        Prim();
    }
    return 0;
}