C++

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

const int MAXSIZE = 100010;
int n, m;
vector<vector<int> > graph(MAXSIZE, vector<int>());
vector<int> inDegree(MAXSIZE, 0), topoRes;

void addEdge(int from, int to) {
    graph[from].push_back(to);
    ++inDegree[to];
}

bool topoSort() {
    queue<int> q;
    for (int i = 1; i <= n; ++i) {
        if (inDegree[i] == 0) {
            q.push(i);
        }
    }

    while (!q.empty()) {
        int v = q.front();
        q.pop();
        topoRes.push_back(v);
        for (int u : graph[v]) {
            --inDegree[u];
            if (inDegree[u] == 0) {
                q.push(u);
            }
        }
        // graph[v].clear();
    }

    return topoRes.size() == n;
}

int main() {
    int x, y;
    cin >> n >> m;
    while (m--) {
        cin >> x >> y;
        if (x == y) {
            cout << -1 << endl;
            return 0;
        }
        addEdge(x, y);
    }

    if (topoSort()) {
        for (int v : topoRes) {
            cout << v << " ";
        }
    } else {
        cout << -1 << endl;
    }

    return 0;
}