topological_sorting(BFS)

#include <bits/stdc++.h>
using namespace std;

const int N = 1e5 + 5; // Adjust based on constraints
vector<int> adj[N];
int indegree[N];
vector<int> ans;

void topological_sort(int n) {
    queue<int> q;

    // Push all nodes with indegree 0
    for (int i = 1; i <= n; i++) {
        if (indegree[i] == 0)
            q.push(i);
    }

    while (!q.empty()) {
        int u = q.front();
        q.pop();
        ans.push_back(u);

        for (int v : adj[u]) {
            indegree[v]--;
            if (indegree[v] == 0)
                q.push(v);
        }
    }

    // If topological sorting is not possible (i.e., cycle exists)
    if (ans.size() != n) {
        cout << "Cycle detected! Topological sorting not possible." << endl;
        return;
    }

    // Print topological order
    for (int node : ans)
        cout << node << " ";
    cout << endl;
}

int main() {
    int n, m;
    cin >> n >> m; // Number of nodes and edges

    // Read edges
    for (int i = 0; i < m; i++) {
        int u, v;
        cin >> u >> v;
        adj[u].push_back(v);
        indegree[v]++;
    }

    topological_sort(n);

    return 0;
}