【Luogu3366】【模板】最小生成树

problem

solution

codes

#include<iostream>
#include<algorithm>
#define maxn 200020
using namespace std;
int n, m;
struct UndirectedEdge{
    int u, v, w;
    UndirectedEdge(){}
    UndirectedEdge(int u, int v, int w): u(u),v(v),w(w){}
    bool operator < (const UndirectedEdge & other)const{
        return w < other.w;
    }
}edges[maxn];
struct UnionFindSet{
    int fa[maxn];
    UnionFindSet(int n){
        for(int i = 1; i <= n; i++)fa[i] = i;
    }
    int find(int x){  return fa[x]==x ? x : fa[x]=find(fa[x]);  }
    void merge(int x, int y){
        int xx = find(x), yy = find(y);
        if(xx != yy)fa[xx] = yy;
    }
};
inline int kruskal(){
    int sum = 0,  count = 0;
    UnionFindSet ufs(n);
    std::sort(edges, edges+m);
    for(int i = 1; i <= m; i++){
        if(ufs.find(edges[i].u) != ufs.find(edges[i].v)){
            ufs.merge(edges[i].u,edges[i].v);
            sum += edges[i].w;
            count++;
            if(count == n-1) break;
        }
    }
    return sum;
}

int main(){
    cin>>n>>m;
    for(int i = 1; i <= m; i++)
        cin>>edges[i].u>>edges[i].v>>edges[i].w;
    cout<<kruskal()<<"\n";
}