Course Schedule

input/code.cpp: In function 'int main()':
input/code.cpp:45:22: warning: comparison of integer expressions of different signedness: 'std::vector<int>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare]
   45 |     if (order.size() == n) {
      |         ~~~~~~~~~~~~~^~~~

#include <iostream>
#include <vector>
#include <queue>

using namespace std;

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int n, m;
    cin >> n >> m;

    vector<vector<int>> adj(n + 1);
    vector<int> in_degree(n + 1, 0);

    for (int i = 0; i < m; ++i) {
        int a, b;
        cin >> a >> b;
        adj[a].push_back(b);
        in_degree[b]++;
    }

    queue<int> q;
    for (int i = 1; i <= n; ++i) {
        if (in_degree[i] == 0) {
            q.push(i);
        }
    }

    vector<int> order;
    while (!q.empty()) {
        int node = q.front();
        q.pop();
        order.push_back(node);

        for (int neighbor : adj[node]) {
            in_degree[neighbor]--;
            if (in_degree[neighbor] == 0) {
                q.push(neighbor);
            }
        }
    }

    if (order.size() == n) {
        for (int course : order) {
            cout << course << " ";
        }
        cout << endl;
    } else {
        cout << "IMPOSSIBLE" << endl;
    }

    return 0;
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED

Test 14

Verdict: ACCEPTED

Test 15

Verdict: ACCEPTED

Test 16

Verdict: ACCEPTED

Test 17

Verdict: ACCEPTED