数据结构-图基础-kruskal

#include<bits/stdc++.h>
using namespace std;
const int N = 100010;
struct edge{
    int a, b, c;
    bool operator<(const edge& w){
        return c < w.c;
    }
}ed[2 * N];
int p[N], n, m;
//并查集
int find(int x){
    if(x == p[x]) return x;
    else return p[x] = find(p[x]);
}
int kruskal(){
    for(int i = 1; i <= n; i++) p[i] = i;
    sort(ed, ed + m);
    int ans = 0, cnt = 0;
    for(int i = 0; i < m; i++){
        int a = ed[i].a, b = ed[i].b;
        if(find(a) != find(b)){
            p[find(a)] = find(b);
            ans += ed[i].c;
            cnt++;
        }
    }
    if(cnt == n - 1) return ans;
    else return -1;
}
int main(){
    cin >> n >> m;
    for(int i = 0; i < m; i++){
        int a, b, c;
        cin >> a >> b >> c;
        ed[i] = {a, b, c};
    }
    int ans = kruskal();
    if(ans == -1) printf("impossible");
    else printf("%d\n", ans);
    return 0;
}