Course Schedule [in O(V+E)]

class Solution {
public:

    vector<unordered_set<int>> make_graph(int numCourses, vector<vector<int>> &prerequisites){
        vector<unordered_set<int>> myGraph(numCourses);
        for(auto &x: prerequisites){
            myGraph[x[1]].insert(x[0]);
        }
        return myGraph;
    }

    bool canFinish(int numCourses, vector<vector<int>>& prerequisites) {
        vector<unordered_set<int>> myGraph = make_graph(numCourses, prerequisites);
        vector<int> inDegrees(numCourses);

        for(auto &x: myGraph){
            for(auto &y: x){
                inDegrees[y]++;
            }
        }

        queue<int> q;

        int c = 0;

        for(int i=0; i<inDegrees.size(); i++){
            if(inDegrees[i]==0){
                c++;
                q.push(i);
            }
        }

        while(!q.empty()){
            //currently queue contains all the nodes with indegree of zero
            //we have to pop them and update the neighbors indegrees and push them accordingly
            int qSize = q.size();
            while(qSize--){
                int fr = q.front();
                q.pop();
                for(auto &x: myGraph[fr]){
                    inDegrees[x]--;
                    if(inDegrees[x]==0){
                        c++;
                        q.push(x);
                    }
                }
            }
        }

        //c is the count of the nodes which have final Indegree as 0
        return (c==numCourses);
    }
};