还是畅通工程 -- prim算法

#include <stdio.h>
#include <string.h>
#define INF 100000000
int map[101][101];
int dis[101];
int vis[101];
int n;

long long ans = 0;
void prim()
{
    int i,j;
    int min,pos;
    memset(vis,0,sizeof(vis));
    memset(dis,INF,sizeof(INF));
    vis[1] = 1;
    dis[1] = 0;
    for(i = 1;i<=n;i++)
    {
        dis[i] = map[1][i];
    }

    min = INF;
    for(i = 1;i<=n-1;i++)
    {
        min = INF;
        for(j = 1;j<=n;j++)
        {
            if(!vis[j] && dis[j]<min)
            {
                pos = j;
                min = dis[j];
            }
        }
        vis[pos] = 1;
        ans = ans + min;
        for(j = 1;j<=n;j++)
        {
            if(!vis[j] && dis[j]>map[pos][j])
            dis[j] = map[pos][j];
        }
    }
}
int main()
{
    int i,j;
    int u,v,w;
    while(scanf("%d",&n),n)
    {
        for(i = 1;i<=n;i++)
        {
            for(j = 1;j<=n;j++)
            {
                if(i == j)
                map[i][j] = 0;
                else
                map[i][j] = INF;
            }
        }
        for(i = 1;i<=(n*(n-1))/2;i++)
        {
            scanf("%d%d%d",&u,&v,&w);
            {
                if(map[u][v]>w)
                {
                    map[u][v] = map[v][u] = w;
                }
            }
        }
        prim();
        printf("%lld
",ans);
        ans = 0;
    }
}