Topological Sort (BFS / Kahn's Algorithm)

class Solution {
  public:
    vector<int> topoSort(int v, vector<vector<int>>& edges) {
        vector<vector<int>>adj(v);
        vector<int>indegree(v);
        
        for(auto ele:edges){
            adj[ele[0]].push_back(ele[1]);
            indegree[ele[1]]++;
        }
        
        queue<int>q;
        
        for(int i=0;i<v;i++){
            if(indegree[i]==0){
                q.push(i);
            }
        }
        
        vector<int>ans;
        
        while(!q.empty()){
            int curr = q.front();
            q.pop();
            
            for(auto ele:adj[curr]){
                indegree[ele]--;
                if(indegree[ele]==0){
                    q.push(ele);
                }
            }
            
            ans.push_back(curr);
        }
        
        return ans;
    }
};