Graphs/KahnAlgorithm.cpp at main · AdityaSharma224/Graphs · GitHub

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


//TC-> O(N+E)
//SC-> O(N)+O(N)
vector<int>topo(int n,vector<int>adj[])
{
    queue<int>q;
    vector<int>indegree(n,0);
    for(int i=0;i<n;i++)
    {
        for(auto it:adj[i])
        {
            indegree[it]++;
        }
    }

    for(int i=0;i<n;i++)
    {
        if(indegree[i]==0)
        {
            q.push(i);
        }
    }

    vector<int>topo;
    while(!q.empty())
    {
        int node = q.front();
        q.pop();

        topo.push_back(node);
        for(auto it:adj[node])
        {
            indegree[it]--;
            if(indegree[it]==0)
            {
                q.push(it);
            }
        }
    }
    return topo;
}

int main()
{
    int n,m;
    cin>>n>>m;
    vector<int>adj[n];
    for(int i=0;i<n;i++)
    {
        int u,v;
        cin>>u>>v;
        adj[u].push_back(v);
    }
    vector<int>ans = topo(n,adj);
    for(int i=0;i<ans.size();i++)
    {
        cout<<ans[i]<<" ";
    }
    cout<<endl;
}