HDU1863---畅通工程

#include<cstdio>
#include<cstring>
#include<cmath>
#include<map>
#include<queue>
#include<iostream>
#include<algorithm>
using namespace std;
const int maxn=102;
int n,m;
int pre[maxn];
struct rode
{
    int x;
    int y;
    int z;
} p[1000];
int compare(rode node1,rode node2) //排序 ，通过值
{
    if(node1.z < node2.z)
        return 1;
    return 0;
}
void hb()//初始化
{
    for(int i=1; i<=n; i++)
        pre[i]=i;
}
int Find(int x)//路径压缩
{
    while(x!=pre[x])
        x=pre[x];
    return x;
}
void uoin(int x,int y)//合并
{
    int fx=Find(x);
    int fy=Find(y);
    if(fx!=fy)
        pre[fx]=fy;
}
int main()
{
    while(scanf("%d%d",&n,&m)&&n)
    { 
        int i;
        for(i=0; i<n; i++)
            scanf("%d%d%d",&p[i].x,&p[i].y,&p[i].z);
        sort(p,p+n,compare);
        hb();
        int minz=0,count=0;
        for (i = 0; i < n; i++)
        {
            if (Find(p[i].x) != Find(p[i].y))
            {
                uoin(p[i].x,p[i].y);
                minz+= p[i].z;
                count++;
                if(count == m-1)
                    break;
            }
        }
        if(count < m-1)
            printf("?\n");
        else
            printf("%d\n", minz);
    }
}