poj 2485 Highways

用kruskal（）算法处理》》。

#include<stdio.h>
#include<stdlib.h>
#define MAXN 300000

int T, n, h, u[MAXN], v[MAXN], w[MAXN], p[510], r[MAXN];

int cmp(const void *_p, const void *_q)
{
    int *p = (int *)_p;
    int *q = (int *)_q;
    return w[*p] - w[*q];
}

int find(int x){return p[x] == x ? x : p[x] = find(p[x]);}

void kruskal()
{
    int ans = 0;
    for(int i = 0; i < n; i ++) p[i] = i;
    for(int i = 0; i < h; i ++) r[i] = i;
    qsort(r,h,sizeof(r[0]),cmp);
    for(int i = 0; i < h; i ++)
    {
        int e = r[i], x = find(u[e]), y = find(v[e]);
        if(x != y){ans = w[e]; p[x] = y;}
    }
    printf("%d\n",ans);
}

int main()
{
    while(~scanf("%d",&T))
    {
        while(T--)
        {
            scanf("%d",&n);
            h = 0;
            for(int i = 0; i < n; i ++)
            {
                for(int j = 0; j < n; j ++)
                {
                    int a;
                    scanf("%d",&a);
                    if(i == j) continue;
                    u[h] = i, v[h] = j, w[h++] = a;
                }
            }
            kruskal();
        }
    }    
}