Course Schedule

#include <bits/stdc++.h>

bool dfs(const int course, const std::vector<std::vector<int>>& graph, std::vector<int>& state, std::vector<int>& order) {
    state[course] = 1;

    for (auto& next : graph[course]) {
        if (state[next] == 0) {
            if (dfs(next, graph, state, order)) {
                return true;
            }
        } else if (state[next] == 1) {
            return true;
        }
    }

    state[course] = 2;
    order.push_back(course);
    return false;
}

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

    int n, m;
    std::cin >> n >> m;

    std::vector<std::vector<int>> graph(n + 1);
    while (m--) {
        int a, b;
        std::cin >> a >> b;
        graph[a].emplace_back(b);
    }

    std::vector state(n+1, 0);
    std::vector<int> order;

    for (int course = 1; course <= n; course++) {
        if (state[course] == 0) {
            if (dfs(course, graph, state, order)) {
                std::cout << "IMPOSSIBLE" << std::endl;
                return 0;
            }
        }
    }

    std::ranges::reverse(order);

    for (const auto& course : order) {
        std::cout << course << ' ';
    }

    std::cout << std::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