TopologicalBfs.cpp

#include< bits/stdc++.h >

using namespace std;

class Graph {
	list <int > *l;
	int V;
	public:
		Graph(int V) {
			this->V = V;
			l = new list<int> [V];
		}

		void addEdge(int x,int y){
			l[x].push_back(y);
		}

		void topolical_sort(){
			int *indegree = new int[V];

           
           for(int i =0; i < V;i++) {
           	indegree[i] = 0;
           }

           for(int i =0; i < V; i++) {
           	   

           	   for(auto y : l[i]) {
           	   	  indegree[y]++;
           	   }
           }
           queue<int > q;
           for(int i = 0; i < V; i++) {
             if(indegree[i] ==0) {
             	q.push(i);
             }
           }
           while(!q.empty()) {
           	int node = q.front();
           	q.pop();
           	cout<< node << endl;
           	for(auto nbr : l[node]) {
           		indegree[nbr]--;
           		if(indegree[nbr]==0) {
           			q.push(nbr);

           		}
           	}
           }
		}
};