TopSortDFS

#include <bits/stdc++.h>
#define maxn 100005

using namespace std;

int n, m, x, y;
vector < int > G[maxn];
list < int > L;
bool viz[maxn];

void read () {
    cin >> n >> m;
    while (m --) {
        cin >> x >> y;
        G[x].emplace_back (y);
    }
}

void dfs (int k) {
    viz[k] = true;
    for (vector < int > :: iterator it = G[k].begin(); it != G[k].end(); ++it)
    if (!viz[*it]) dfs (*it);
    L.push_front (k);
}

void solve () {
    for (int i = 1; i <= n; ++i) if (!viz[i]) dfs (i);
}

void print () {
    for (list < int > :: iterator it = L.begin(); it != L.end(); ++it) cout << *it << " ";
    cout << '\n';
}

int main(){
    read();
    solve();
    print();
    return 0;
}