【模板】最小生成树——Kruskal算法

【模板】最小生成树——Kruskal算法

Kruskal算法（n*n+m）

#include<iostream>
#include<cstring>
#include<cstdio>
#include<string>
#include<queue>
#include<stack>
#include<algorithm>
#include<vector>
#include<map>
using namespace std;
const int INF= 0x3f3f3f3f;
struct MS
{
    int u, v, w;
}gr[500001];
int fa[500100];
int n, m;
bool cmp(MS X,MS Y)
{
    return X.w < Y.w;//结构体重载
}
int findx(int x)//并查集
{
    if(x!=fa[x])
        fa[x] = findx(fa[x]);
    return fa[x];
}
void unity(int x,int y)//祖先合并
{
    int x1 = findx(x);
    int y1 = findx(y);
    if(x1!=y1)
        fa[x1] = y1;
}
void make_out()//初始化并查集
{
    for (int i = 1; i<= n;i++)
       { fa[i] = i;
       }
}
int main()
{
    cin >> n >> m;
    int total = 0;
    for (int i = 1; i<= m;i++)
    {
        cin >> gr[i].u >> gr[i].v >> gr[i].w;
    }
    make_out();
    sort(gr + 1, gr + m + 1, cmp);//根据权值从小到大排序
    for (int i = 1; i<= m;i++)
    {
        int u1 = gr[i].u;
        int v1 = gr[i].v;
        if(findx(u1)!=findx(v1))
        {
            total += gr[i].w;
            unity(u1, v1);
        }
    }
    int ans = 0;
    for (int i = 1; i <= n;i++)
    {
        if(fa[i]!=i)//判断是不是联通图
            ans++;
    }
    if(ans==n-1)
        cout << total;
        else{
            cout << "orz";
        }
    return 0;
}