bzoj 1821: [JSOI2010]Group 部落划分 Group Kruskal

题意

分析

代码

#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<algorithm>
#include<cmath>
using namespace std;

const int N=1005;

int n,m,x
,y
,f
,cnt;
struct edge{int x,y,dis;}e[N*N];

bool cmp(edge a,edge b)
{
return a.dis<b.dis;
}

int find(int x)
{
if (f[x]==x) return x;
else return f[x]=find(f[x]);
}

int main()
{
scanf("%d%d",&n,&m);
for (int i=1;i<=n;i++) scanf("%d%d",&x[i],&y[i]);
for (int i=1;i<n;i++)
for (int j=i+1;j<=n;j++)
e[++cnt].x=i,e[cnt].y=j,e[cnt].dis=(x[i]-x[j])*(x[i]-x[j])+(y[i]-y[j])*(y[i]-y[j]);
sort(e+1,e+cnt+1,cmp);
int s=n;
for (int i=1;i<=n;i++) f[i]=i;
for (int i=1;i<=cnt;i++)
{
int x=find(e[i].x),y=find(e[i].y);
if (x==y) continue;
else if (s==m)
{
printf("%.2lf",sqrt(e[i].dis));
return 0;
}
else f[x]=y,s--;
}
return 0;
}