6 контест 1 задача

#include<iostream>
#include<vector>
#include<algorithm>

using namespace std;
vector<vector<int>> g;
vector<bool> used;
vector<int> min_e;

void prim(int n){
    min_e[0] = 0;
    for (int i = 0; i < n; i++) {
        int v = -1;
        for (int j = 0; j < n; j++) {
            if (!used[j] && (v == -1 || min_e[j] < min_e[v])) {
                v = j;
                break;
            }
        }
        if (v == -1)
            break;
        used[v] = true;
        for (int to = 0; to < n; to++) {
            if (g[v][to] < min_e[to]) {
                min_e[to] = g[v][to];
            }
        }
    }
}

int main() {
    int n, m;
    cin >> n >> m;
    g = vector<vector<int>>(n, vector<int>(n, 1e9));
    used = vector<bool>(n);
    min_e = vector<int>(n, 1e9);
    for (int i = 0; i < m; i++) {
        int fr, to, value;
        cin >> fr >> to >> value;
        fr--;to--;
        g[fr][to] = value;
        g[to][fr] = value;
    }
    prim(n);
    int sum = 0;
    for (auto &i : min_e) {
        sum += i;
    }
    cout << sum;
}