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input/code.cpp: In function 'int main()':
input/code.cpp:104:21: warning: comparison of integer expressions of different signedness: 'std::vector<long long int>::size_type' {aka 'long unsigned int'} and 'long long int' [-Wsign-compare]
  104 |     if(order.size() != n) return 0;
      |        ~~~~~~~~~~~~~^~~~

#include <iostream>
#include <vector>
#include <queue>
#include <climits>
using namespace std;

void dijkstra(const vector<vector<pair<long long,long long>>> &adj, long long start, vector<long long> &dist) {
    long long n = adj.size();
    dist.assign(n, LLONG_MAX);
    vector<bool> processed(n, false);

    priority_queue<pair<long long,long long>, vector<pair<long long,long long>>, greater<pair<long long,long long>>> pq;
    dist[start] = 0;
    pq.push({0, start});

    while (!pq.empty()) {
        long long a = pq.top().second;
        pq.pop();
        if (processed[a]) continue;
        processed[a] = true;

        for (auto [b, w] : adj[a]) {
            if (dist[a] + w < dist[b]) {
                dist[b] = dist[a] + w;
                pq.push({dist[b], b});
            }
        }
    }
}

void topological_sort(const vector<vector<long long>> &adj, vector<long long> &order) {
    int n = adj.size();
    vector<long long> indegree(n, 0);

    for (int u = 0; u < n; u++) {
        for (int v : adj[u]) {
            indegree[v]++;
        }
    }

    queue<int> q;

    for (int i = 0; i < n; i++) {
        if (indegree[i] == 0) q.push(i);
    }

    order.reserve(n);

    while (!q.empty()) {
        int u = q.front();
        q.pop();
        order.push_back(u);


        for (int v : adj[u]) {
            indegree[v]--;
            if (indegree[v] == 0) q.push(v);
        }
    }


    if ((int)order.size() != n) {
        cout << "IMPOSSIBLE" << endl;
        return ;

    }


}


int main() {
    long long n, m;
    cin >> n >> m;
    /*vector<vector<pair<long long,long long>>> adj(n);

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

    vector<long long> dist;
    dijkstra(adj, 0, dist);

    for (long long i = 0; i < n; i++) {
       
        cout << dist[i] << " ";
    }*/
    vector<vector<long long>> adj(n);

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

    }

    vector<long long > order;
    topological_sort(adj, order);
    if(order.size() != n) return 0;
    for(size_t i = 0; i < order.size(); i++){
        cout << order[i] + 1 << " ";
    }

}

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