九度教程第74题

题目地址：http://jobdu.sinaapp.com/problem.php?cid=1040&pid=73

C语言源码：

#include<stdio.h>
#include<stdlib.h>
#define maxsize 110
typedef struct edge
{
	int a,b;
	int weight;
}edge;
edge E[maxsize];
int T[maxsize];
int findroot(int x)
{
	int temp;
	if(T[x]==-1)
		return x;
	else
	{
		temp=findroot(T[x]);
		T[x]=temp;
		return temp;
	}
}
int cmp(const void *a,const void *b)
{
	edge *aa=(edge *)a;
	edge *bb=(edge *)b;
	return aa->weight-bb->weight;
}
int main()
{
	int n,m,weight,i,num,roota,rootb;
	scanf("%d %d",&n,&m);
	while(n)
	{
		for(i=0;i<n;i++)
			scanf("%d %d %d",&E[i].a,&E[i].b,&E[i].weight);
		qsort(E,n,sizeof(E[0]),cmp);
		for(i=1;i<=m;i++)
			T[i]=-1;
		weight=0;
		num=0;
		for(i=0;i<n;i++)
		{
			roota=findroot(E[i].a);
			rootb=findroot(E[i].b);
			if(roota!=rootb)
			{
				T[rootb]=roota;
				weight+=E[i].weight;
			}
		}
		for(i=1;i<=m;i++)
			if(T[i]==-1)
				num++;
		if(num>1)
			printf("?\n");
		else
			printf("%d\n",weight);
		scanf("%d %d",&n,&m);
	}
}