Problem P62138_ca: Ordenacions topològiques

#include <iostream>
#include <vector>
using namespace std;

void escriu_solucio(const vector<int> &sp, int n)
{
    if (n > 0) {
        cout << sp[0];
    }
    for (int i = 1; i < n; i++) {
        cout << " " << sp[i];
    }
    cout << endl;
}

void ordenatopo(const vector<vector<int> > &dep, vector<int> &ge, vector<int> &sp, int n, int m, int q)
{
    if (q == n) {
        escriu_solucio(sp, n);
    } else {
        for (int i = 0; i < n; i++) {
            if (ge[i] == 0) {
                for (int j = 0; j < dep[i].size(); j++) {
                    ge[dep[i][j]]--;
                }

                sp[q] = i;
                ge[i]--; //Used
                ordenatopo(dep, ge, sp, n, m, q+1);
                ge[i]++; //Not used
                sp[q] = -1;

                for (int j = 0; j < dep[i].size(); j++) {
                    ge[dep[i][j]]++;
                }
            }
        }
    }
}


int main()
{
    int n, m;
    cin >> n >> m;

    vector<int> ge(n, 0);
    vector<vector<int> > dep(n);
    for (int i = 0; i < m; i++) {
        int first, second;
        cin >> first >> second;
        dep[first].push_back(second);
        ge[second]++;
    }

    vector<int> sp(n, -1);
    ordenatopo(dep, ge, sp, n, m, 0);
}