hdu 1863 qsort+kruskral

#include<bits/stdc++.h>using namespace std;const int maxn=1e5+5;struct node{int from,to,cost;}edge[maxn];int par[maxn];int find(int num){    return par[num]==num?num:par[num]=find(par[num]);}int cmp(const void *a,const void *b){    return(((node*)a)->cost-((node*)b)->cost);}int main(){    int n,m,i,j;    while(scanf("%d%d",&n,&m)!=EOF&&n)    {        for(i=0;i<=m;i++)            par[i]=i;        for(i=0;i<n;i++)            scanf("%d%d%d",&edge[i].from,&edge[i].to,&edge[i].cost);        qsort(edge,n,sizeof(node),cmp);        int cnt=0,res=0;        for(i=0;i<n;i++)        {            int sa=find(edge[i].from),sb=find(edge[i].to);            if(sa==sb)                continue;            res+=edge[i].cost;            par[sa]=sb;            cnt++;            if(cnt==m-1)                break;        }        if(cnt>=m-1)            printf("%d\n",res);        else            printf("?\n");    }    return 0;}