CSES Problem Set Course Schedule Solution

Problem Link: https://cses.fi/problemset/task/1679

Solution in C++:

/// La ilaha illellahu muhammadur rasulullah

///******Bismillahir-Rahmanir-Rahim******///

/// Abul Hasnat Tonmoy

/// Department of CSE,23rd batch

/// Islamic University,Bangladesh

///**********ALLAH IS ALMIGHTY************///

#include <bits/stdc++.h>

using namespace std;

const int N = 1e5 + 5;

std::vector<int> g[N];

vector<int> ans;

bool cycle;

int col[N];

void dfs(int u) {

col[u] = 1;

for (auto v : g[u]) {

if (col[v] == 0) {

dfs(v);

} else if (col[v] == 1)

cycle = true;

}

col[u] = 2;

ans.push_back(u);

}

int main() {

int n, e;

cin >> n >> e;

while (e--) {

int u, v;

cin >> u >> v;

g[u].push_back(v);

}

cycle = false;

for (int i = 1; i <= n; i++) {

if (col[i] == 0) dfs(i);

}

if (cycle == true)

cout << "IMPOSSIBLE" << endl;

else {

reverse(ans.begin(), ans.end());

for (auto i : ans) {

cout << i << " ";

}

cout << endl;

}

}