kruskal

https://www.luogu.org/wiki/show?name=%E9%A2%98%E8%A7%A3+P3366

据说kruskal比prim快
其实kruskal有很多的应用，因为它是建立在并查集上的

#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cmath>
#include<cstring>
#include<algorithm>
#include<cstring>
#include<string>
#define Ll long long
using namespace std;
struct cs{
    int x,y,z;
}a[200001];
int father[5001];
int n,m,xx,yy,ans;
bool cmp(cs a,cs b){
    return a.z<b.z;
}
int getfa(int x){
    if(father[x]==x)return x;
    father[x]=getfa(father[x]);
    return father[x];
}
int main()
{
    scanf("%d%d",&n,&m);
    for(int i=1;i<=m;i++)scanf("%d%d%d",&a[i].x,&a[i].y,&a[i].z);
    sort(a+1,a+m+1,cmp);
    for(int i=1;i<=n;i++)father[i]=i;
    for(int i=1;i<=m;i++){
        xx=getfa(a[i].x);
        yy=getfa(a[i].y);
        if(xx==yy)continue;
        ans+=a[i].z;
        father[xx]=yy;
    }
    cout<<ans;
}