POJ 2485 Highways【最小生成树】

//9188632	ylwh	2485	Accepted	632K	188MS	G++	1066B	2011-08-18 17:15:42
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <math.h>
#include <algorithm>
using namespace std;
#define N 501
struct edge
{
	int x, y, len;
}e[N * N / 2];
int root[N];
int find_root(int x)
{
	int temp = x;
	while(temp != root[temp])
		temp = root[temp];
	root[x] = temp;
	return temp;
}
int cmp(struct edge a, struct edge b)
{
	return a.len < b.len;
}
int main()
{
	int t, n, i, j, a, b, cnt, x, y, temp, ans;
	scanf("%d", &t);
	while(t--)
	{
		cnt = -1;
		ans = 0;
		scanf("%d", &n);
		for(i=1; i<=n; i++)
			root[i] = i;
		for(i=1; i<=n; i++)
			for(j=1; j<=n; j++)
			{
				scanf("%d", &temp);
				if(j > i)
				{
					e[++cnt].x = i;
					e[  cnt].y = j;
					e[  cnt].len = temp;
				}
			}
		sort(e, e + cnt + 1, cmp);
		for(i=0; i<=cnt; i++)
		{
			a = find_root(e[i].x);
			b = find_root(e[i].y);
			if(a != b)
			{
				if(e[i].len > ans)
					ans = e[i].len;
				if(a > b)
					root[a] = b;
				else
					root[b] = a;
			}
		}
		printf("%d\n", ans);
	}
    return 0;
}