CourseSchedule-II.cpp

class Solution {
public:
    vector<int> findOrder(int N, vector<vector<int>>& prerequisites) {
         vector<int>adj[N];
	    for(auto i:prerequisites){
	        adj[i[1]].push_back(i[0]);
	    }
	        vector<int>indegree(N,0);
	        for(int i=0;i<N;i++){
	            for(auto it:adj[i]){
	                indegree[it]++;
	            }
	        }
	        queue<int>q;
	        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);
	                }
	            }
	        }
	    
	    if(topo.size()==N){
	        return topo;
	    }
	    return {};
    }
};