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 longusing 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;}