ЗОШ Unique TopSOrt Idee

#include <iostream>
#include <cmath>
#include <vector>
#include <queue>
#include <algorithm>
#include <string>
#include <stack>
#include <set>
#include <map>
#define pii pair <int,int>
using namespace std;
using ll = long long;
using ld = long double;
void cv(vector <int> &v){
    for (auto x: v) cout<<x<<' ';
    cout<<"\n";
}

void cvl(vector <ll> &v){
    for (auto x: v) cout<<x<<' ';
    cout<<"\n";
}


void cvv(vector <vector <int> > &v){
    for (auto x: v) cv(x);
    cout<<"\n";
}
int n,m;
vector <vector<int>>G;
const int wh = 0, gr = 1, bl = 2;
vector <int> clr;
vector <int> tp;

//int cnt = 0;//connected
void dfs(int v, int pr){
    clr[v] = gr;
    for (int u: G[v]){
        if (u == pr) continue;
        else if (clr[u] == wh){
            dfs(u, v);
            for (int x: G[v]){
                if (clr[x] != bl){
                    cout<<"NO\n";
                    exit(0);
                }
            }
        }
        else if (clr[u] == gr){
            cout<<"NO\n";
            exit(0);
        }
    }
    clr[v] = bl;
    tp.push_back(v+1);
}




int main()
{
    ios::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	cin>>n>>m;
	G.resize(n);
	clr.assign(n, wh);
	vector <int> in(n,0), out(n, 0);
	bool can = 1;
	for (int i=0;i<m;++i){
        int a,b; cin>>a>>b;
        a--; b--;
        G[a].push_back(b);
        in[b]++;
        out[a]++;
	}
	if (count(in.begin(), in.end(), 0) != 1){
        can  = 0;
	}
	if (count(out.begin(), out.end(), 0) != 1){
        can = 0;
	}
	if (!can){
        cout<<"NO\n";
        exit(0);
	}
	for (int i = 0;i<n;++i){
        if (clr[i] == wh){
            dfs(i, -1);
        }
	}
	cout<<"YES\n";
	reverse(tp.begin(), tp.end());
	cv(tp);
}
/*
КОНТРПРИМЕР:
3 3
1 2
2 3
1 3
YES
1 2 3
*/