A solution to a graph theory CF practice problem in C++

problem_b.cpp

#include <bits/stdc++.h>
#define N 1000010
using namespace std;
typedef long long int ll;

vector<ll> graph[N];
set<ll> seen;
ll min_cost = LLONG_MAX;

void dfs(ll costs[], ll r) {
    seen.insert(r);
    if (costs[r] < min_cost) min_cost = costs[r];

    for (ll i : graph[r]) if (!seen.count(i)) dfs(costs, i);
}

int main() {
    ll n, m, u, v;
    cin >> n >> m;
    ll c[n + 1];

    for (int i = 1; i < n + 1; i++) cin >> c[i];

    for (int i = 0; i < m; i++) {
        cin >> u >> v;

        graph[u].push_back(v);
        graph[v].push_back(u);
    }

    ll cost = 0;
    
    for (int i = 1; i <= n; i++) {
        if (!seen.count(i)) { 
            min_cost = c[i];
            dfs(c, i);
            cost += min_cost;
        }
    }
    cout << cost << endl;
}