Highways(prim)

http://poj.org/problem?id=2485

此题是求最小生成树里的最大权值。prim算法：

#include<stdio.h>
#include<string.h>
const int maxn=505;
const int INF = 1<<28;
int map[maxn][maxn];
int dis[maxn],vis[maxn];
int n,maxm;
void prim()
{
    int pos;
    for (int i = 1; i <= n; i ++)
    {
        dis[i] = map[1][i];
    }
    vis[1] = 1;
    for (int i = 1; i <= n-1; i ++)
    {
        int min = INF;
        for (int j = 1; j <= n; j ++)
        {
            if (!vis[j] && dis[j] < min)
            {
                min = dis[j];
                pos = j;
            }
        }
        if(min > maxm)
        {
            maxm = min;
        }
        vis[pos] = 1;
        for (int j = 1; j <= n; j ++)
        {
            if (!vis[j] && dis[j] > map[pos][j])
                dis[j] = map[pos][j];
        }
    }
}
void init()
{
    maxm = -1;
    for (int i = 0; i <= n; i ++)
    {
        for (int j = 0; j <= n; j ++)
        {
            map[i][j] = INF;
        }
        map[i][i] = 0;
        vis[i] = 0;
    }
}
int main()
{
    int t;
    scanf("%d",&t);
    while(t--)
    {
        scanf("%d",&n);
        init();
        for (int i = 1; i <= n; i ++)
        {
            for (int j = 1; j <= n; j ++)
            {
                scanf("%d",&map[i][j]);
            }
        }
        prim();
        printf("%d
",maxm);
    }
    return 0;
}