1408081640-hd-畅通工程.cpp

#include<stdio.h>
#include<stdlib.h>
#include<algorithm>
using namespace std;
int town[110];
struct road
{
    int x,y,q;
}roads[5000];
bool cmp(road a, road b)
{
    return a.q<b.q;
}
int find(int a)
{
    if(town[a]==a)
        return a;
    else
        return find(town[a]);
}
int main()
{
    int n,m;
    int i,j,k,sum,num;
    while(scanf("%d%d",&n,&m),n)
    {
        for(i=0;i<=m;i++)
            town[i]=i;
        for(i=0;i<n;i++)
            scanf("%d%d%d",&roads[i].x,&roads[i].y,&roads[i].q);
        sort(roads,roads+n,cmp);
        sum=0;
        for(i=0;i<n;i++)
        {
            j=find(roads[i].x);
            k=find(roads[i].y);
            if(j!=k)
            {
                town[j]=k;
                sum+=roads[i].q;
            }
        }
        num=0;
        for(i=1;i<=m;i++)
            if(town[i]==i)
                num++;
        if(num==1)
            printf("%d\n",sum);
        else
            printf("?\n");
    }
    return 0;
}