poj1797最大生成树

//1348K	454MS
//注意不是生成整棵树而是只要可以到达N点就行了
#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))//能到达N点就行了
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;
}