poj 2485 Highways 最小生成树

//poj 2485 Highways
//MST(minimum spanning tree)
//here is want to get the longest road

#include <stdio.h>
#include <string.h>

#define N 505
#define INF 1<<30

int n;
int map[N][N], dis[N], ans;
bool vis[N];

void prim()
{
    for(int i = 0; i < n; ++i)
    {
        dis[i] = INF;
        vis[i] = false;
    }
    dis[0] = 0;
    while(1)
    {
        int min = INF, index = -1;
        for(int i = 0; i < n; ++i)
        {
            if(vis[i] == false && min > dis[i])
            {
                min = dis[i];
                index = i;
            }
        }
        if(index == -1)
            return;
        vis[index] = true;

        if(ans < min)   //保存MST中的最长路
            ans = min;

        for(int i = 0; i < n; ++i)
            if(vis[i] == false && dis[i] > map[index][i])
                dis[i] = map[index][i];
    }
}

int main()
{
    int n_case;
    scanf("%d", &n_case);
    while(n_case--)
    {
        ans = 0;
        memset(map, 0, sizeof(map));
        scanf("%d", &n);
        for(int i = 0; i < n; ++i)
        {
            for(int j = 0; j < n; ++j)
            {
                scanf("%d", &map[i][j]);
                map[j][i] = map[i][j];
            }
        }
        prim();
        printf("%d\n", ans);
    }
    return 0;
}