原題傳送門

水一題，此題和洛谷P4047 [JSOI2010]部落劃分完全一樣，沒有任何區別，程式碼就調換了一下n和m輸入的順序以及最後while(ans>=m)改成了while(ans>m)

題解傳送門

#include<bits/stdc++.h>
#define INF 2147483647
using namespace std;
int dad[5003];
struct node{
    int num,to;
    int value;
};
int find(int x){
    if(dad[x]==x) return x;
    dad[x]=find(dad[x]);
    
 
return dad[x];
}
bool operator < (const node &a, const node &b){
    return a.value > b.value;
} 
int main(){
    vector<node>a[5003];
    int ax[1003],ay[1003];
    priority_queue<node> q;
    int n,m,i,x,y,z,ans,ansn;
    node t;t.value=INF;
    memset(dad,0,sizeof(dad));
    cin
 
>>m>>n;
    for(i=1;i<=n;i++){
        dad[i]=i;
        scanf("%d%d",&ax[i],&ay[i]);
        for(int j=1;j<i;j++){
            node b;
            b.num=i;b.to=j;b.value=(ax[i]-ax[j])*(ax[i]-ax[j])+(ay[i]-ay[j])*(ay[i]-ay[j]);
            q.push(b);
        }
    }
    ans
 
=n;node b;
    while(ans>m){
        b=q.top();q.pop();x=b.to;
        if(find(x)==find(b.num)) continue;
        dad[find(x)]=b.num;ans--;
//        printf("%d->%d:%d\n",b.num,b.to,b.value);
    }
    printf("%.2lf",sqrt(b.value));
}