Comments

• 
  

  0

  

  oryshych_d  commented on June 27, 2025, 7:50 a.m.

  include <algorithm>

  include <iostream>

  include <queue>

  include <vector>

  using std::cout; using std::endl; using std::vector;

  int main() { int n, m; std::cin >> n >> m;

  vector<vector<int>> graph(n);
  for (int i = 0; i < m; i++) {
      int a, b;
      std::cin >> a >> b;
      graph[a - 1].push_back(b - 1);
  }
  
  vector<int> in_degree(n);
  for (const vector<int> &nodes : graph) {
      for (int node : nodes) { in_degree[node]++; }
  }
  
  std::queue<int> queue;
  for (int i = 0; i < n; i++) {
      if (in_degree[i] == 0) { queue.push(i); }
  }
  vector<int> top_sort;
  while (!queue.empty()) {
      int curr = queue.front();
      queue.pop();
      top_sort.push_back(curr);
      for (int next : graph[curr]) {
          if (--in_degree[next] == 0) { queue.push(next); }
      }
  }
  
  if (top_sort.size() == n) {
      for (int i = 0; i < n - 1; i++) { cout << top_sort[i] + 1 << ' '; }
      cout << top_sort.back() + 1 << endl;
  } else {
      cout << "IMPOSSIBLE" << endl;
  }

  }