CSES – Road Reparation

#include<bits/stdc++.h>
#define int long long
#define f first
#define s second
#define fastio ios_base::sync_with_stdio(0);cin.tie(0)
using namespace std;
//declare
const int maxn = 1e5+5;
int n,m;
//
struct DSU{
    int boss[maxn];
    int components;
    DSU(int _n): components(_n) {
        for(int i=1;i<=_n;i++){
            boss[i] = i;
        }
    }
    int find(int a){
        return (a == boss[a] ? a : boss[a] = find(boss[a]));
    }
    void join(int a,int b){
        a = find(a), b = find(b);
        if(a == b) return;
        boss[a] = b;
        components--;
    }
    bool same(int a,int b){
        return find(a) == find(b);
    }
};
signed main(){
    fastio;
    cin>>n>>m;
    DSU d(n);
    vector<array<int,3>> v;
    for(int i=0;i<m;i++){
        int a,b,c; cin>>a>>b>>c;
        v.push_back({c,a,b});
    }
    sort(v.begin(),v.end());
    int cost = 0;
    for(auto &[c,a,b] : v){
        if(!d.same(a,b)){
            d.join(a,b);
            cost += c;
        }
    }
    if(d.components != 1) cout<<"IMPOSSIBLE\n";
    else cout<<cost<<"\n";
    return 0;
}