CourseSchedule-I.cpp

class Solution {
public:
    bool canFinish(int numCourses, vector<vector<int>>& prerequisites) {
         vector<int>adj[numCourses];
	    for(auto i:prerequisites){
	        adj[i[0]].push_back(i[1]);
	    }
	        vector<int>indegree(numCourses,0);
	        for(int i=0;i<numCourses;i++){
	            for(auto it:adj[i]){
	                indegree[it]++;
	            }
	        }
	        queue<int>q;
	        for(int i=0;i<numCourses;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()==numCourses){
	        return true;
	    }
	    return false;
    }
};