Course Schedule

input/code.cpp: In function 'std::vector<int> dfs(std::vector<std::vector<int> >&)':
input/code.cpp:34:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   34 |     for (int i = 1; i < adj.size(); i++) {
      |                     ~~^~~~~~~~~~~~

#include <iostream>
#include <vector>
#include <cmath>
#include <bits/stdc++.h>

using namespace std;

int dfsRec(vector<vector<int>> &adj, 
vector<int> &visited, int s, vector<int> &res) {
    
    visited[s] = 1;
    int loop = 0;

    // Recursively visit all adjacent 
    // vertices that are not visited yet
    for (int i : adj[s])
    {
        if (visited[i] == 0)
            loop = dfsRec(adj, visited, i, res);
        if (visited[i] == 1)
            return 1;            
    }
    res.push_back(s);
    visited[s] = 2;
    return loop;
}

vector<int> dfs(vector<vector<int>> &adj) {
    vector<int> visited(adj.size(), 0);
    vector<int> res;
    int loop = 0;
    // Loop through all vertices 
    // to handle disconnected graph
    for (int i = 1; i < adj.size(); i++) {
        if (visited[i] == 0) {
            loop |= dfsRec(adj, visited, i, res);
        }
    }
    if(loop == 1)
    {
        cout << "IMPOSSIBLE";
        return {};
    }
    return res;
}
//Driver Code Starts

void addEdge(vector<vector<int>>& adj, int u, int v) {
    adj[u].push_back(v);
    adj[v].push_back(u);
}


int main()
{
    long long n_courses;
    long long requirements;
    cin >> n_courses >> requirements;

    vector<vector<int>> graph(n_courses + 1);
    for(int i = 0; i < requirements; ++i)
    {
        int a, b;
        cin >> a >> b;
        graph[a].push_back(b);
    }

    vector<int> res = dfs(graph);

    for(int i = res.size() - 1; i >= 0; --i)
    {
        cout << res[i] << " ";
    }
    cout << endl;

}

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