最小生成树 kruscal 堆优化 板子

每次都取出权值最小的边 并且保证他不会出现环(用并查集维护)

最小边用堆维护

#include<bits/stdc++.h>
#include<iostream>

using namespace std;
typedef long long ll;
typedef pair<ll,ll> P;
const int NS=5e5+10;
int dir[4][2]={{1,0},{-1,0},{0,1},{0,-1}};
ll mod=19260817;
struct E
{
   ll to,w,next=-1,start;
}e[500005];
ll head[5005];
ll cha[5005];
ll ge[5005];
ll dis[200005];
bool flag[200005];
struct cmp
{
    bool operator()(P a,P b)
    {
        return a.second>b.second;
    }
};
int finds(int a)
{
    if(cha[a]==a)
        return a;
    else
    {
        cha[a]=finds(cha[a]);
        return cha[a];
    }
}

void unions(int a,int b)
{
    int aa=finds(a);
    int bb=finds(b);
    if(aa==bb)
        return ;
    else
    {
        cha[aa]=bb;
        ge[bb]+=ge[aa];
    }
}
priority_queue< P,vector<P>,cmp> que;
int main()
{

    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int n,m;
    cin>>n>>m;
    for(int i=1;i<=n;i++)
    {
        cha[i]=i;
        ge[i]=1;
    }
    int heads=1;
    while(m--)
    {
        ll temp,s,t;
        cin>>s>>t>>temp;
        e[heads].start=s;
        e[heads].to=t;
        P a(heads,temp);
        heads++;
        que.push(a);
    }
    ll sum=0,flag=1;
    while(!que.empty())
    {
        P temp=que.top();
        que.pop();
        int edge=temp.first;
        if(finds(e[edge].start)==finds(e[edge].to))
            continue;
        sum+=temp.second;
        unions(e[edge].start,e[edge].to);
        if(ge[finds(e[edge].start)]==n||ge[finds(e[edge].to)]==n)
          {
              flag=0;
            break;}
    }
    if(flag)
        cout<<"orz";
        else
            cout<<sum;


}