poj1797最大生成樹

//1348K	454MS	
//注意不是生成整棵樹而是隻要可以到達N點就行了
#include <iostream>
#include <stdio.h>
#include <string.h>
#include <algorithm>
using namespace std;

#define  MAXE  1000005
#define  MAXN  1006


static struct edge
{
	int from;
	int to;
	int cost;
}Edge[MAXE];
static int E;
static int cmp(const edge&ls,const edge&rs)
{
	return ls.cost>rs.cost;
}
static int par[MAXN];
static int N;
static void init()
{
	for (int i=0;i<N;++i)
	 par[i] = i;
}
static int getParent(int i)
{
	if (par[i]!=i)
	 par[i] = getParent(par[i]);
	return par[i];
}

static void merge(int u,int v)
{
	int p1 = getParent(u);
	int p2 = getParent(v);
	if (p1==p2)
	 return;
	par[p1] = p2;
}

static bool same(int u,int v)
{
	int p1 = getParent(u);
	int p2 = getParent(v);
	if (p1==p2)
	 return true;
	return false;
}

static void addEdge(int from,int to,int cost)
{
	Edge[E].from = from;
	Edge[E].to = to;
	Edge[E].cost = cost;
	E++;
}

static int krustral()
{
	sort(Edge,Edge+E,cmp);
	int ans = -1;
	int res = 0;
	for (int i=0;i<E;++i)
	{
		if (same(0,N-1))//能到達N點就行了
		 break;
		edge e = Edge[i];
		if (!same(e.from,e.to))
		{
			ans = e.cost;
			merge(e.from,e.to);
		}
	}
	printf("%d\n",ans);
	printf("\n");
	return res;
}

int main()
{
	int T;
	scanf("%d",&T);
	int ncase = 1;
	int es;
	while(T--)
	{
		scanf("%d %d",&N,&es);
		int u,v,c;
		E = 0;
		for (int i=0;i<es;++i)
		{
			scanf("%d %d %d",&u,&v,&c);
			addEdge(u-1,v-1,c);
			addEdge(v-1,u-1,c);
		}
		init();
		printf("Scenario #%d:\n",ncase);
		ncase++;
		krustral();
	}
	return 0;
}