Course Schedule

#include <bits/stdc++.h>

using namespace std;

//Definitions for quicker writing
#define REP(i,a,b) for (int i = a; i < b; i++)
#define PB push_back

//Typedefs for quicker writing
typedef long long ll;
typedef vector<int> vi;
typedef pair<int,int> pi;

int imx = 1e5+7;

vector<vi> req(imx);
vi proc(imx,0);
vi order;

bool dfs(int cur){
	proc[cur] = 1;
	for(auto next: req[cur]){
		if(proc[next] == 1){
			return false;
		}	
		else if(proc[next] == 0){
			if(!dfs(next)){
				return false;
			}
		}
	}
	proc[cur] = 2;
	order.PB(cur);
	return true;
	
}

int main() {
	//IO optimization
	ios::sync_with_stdio(0);
	cin.tie(0);
	
	//Input definition
	int n;
	int m;

	//Read In
	cin >> n >> m;
	
	//Initialize adj list
	REP(i,0,m){
		int a,b;
	       	cin >> a >> b;
		req[a].PB(b);
	}

	//Main part
	bool imp = false;

	REP(i,1,n+1){
		if(proc[i]==0){
			if(!dfs(i)){
				imp = true;
				break;
			}
		}
	}
	
	//Write out
	if(imp){
		cout << "IMPOSSIBLE" << "\n";
	} 
	else{
		REP(i,1,n+1){
			cout << order[n-i] << " ";
		}
		cout << endl;
	}
		
	//Return
	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