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krushkalsalgoin2dplane.cpp
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krushkalsalgoin2dplane.cpp
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#include<iostream>
#include<vector>
#include<bits/stdc++.h>
#define lli long long int
#define mod 1000000007
#define pb push_back
#define mk make_pair
#define fastio ios_base::sync_with_stdio(false); cout.tie(NULL);
using namespace std;
vector<int> par(100001,-1);
struct edge
{
int a,b;
double w;
}ar[100001];
bool comp(edge a,edge b)
{
if(a.w<b.w)
return true;
return false;
}
int find(int a)
{
if(par[a]<0)
return a;
return par[a]=find(par[a]);
}
void Union(int a,int b)
{
par[b]=a;
}
int main()
{
fastio;
int n,i,j,a,b,c=0;
double ans=0;
cin>>n;
int x[n],y[n];
cout<<fixed<<setprecision(8);
for(i=0;i<n;i++)
cin>>x[i]>>y[i];
for(i=0;i<n-1;i++)
{
for(j=i+1;j<n;j++)
{
ar[c].a=i+1;
ar[c].b=j+1;
ar[c].w=sqrt(pow(x[i]-x[j],2)+pow(y[i]-y[j],2));
c++;
ar[c].a=j+1;
ar[c].b=i+1;
ar[c].w=ar[c-1].w;
c++;
}
}
sort(ar,ar+c,comp);
// for(i=0;i<c;i++)
// cout<<ar[i].a<<" "<<ar[i].b<<" "<<ar[i].w<<endl;
for(i=0;i<c;i++)
{
a=find(ar[i].a);
b=find(ar[i].b);
if(a!=b)
{
ans+=ar[i].w;
Union(a,b);
// cout<<endl<<ar[i].a<<" "<<ar[i].b<<" "<<ar[i].w<<endl;
}
}
cout<<ans;
return 0;
}