207. Course Schedule

class Solution {
public:
    bool canFinish(int numCourses, vector<pair<int, int>>& prerequisites) {
        vector<vector<int>> graph(numCourses,vector<int>(0));
        vector<int> inDegree(numCourses,0);
        for(auto i : prerequisites){
            graph[i.second].push_back(i.first);
            inDegree[i.first]++;
        }
        
        queue<int> q;
        for(int i = 0;i < numCourses;i++){
            if(inDegree[i] == 0)
                q.push(i);
        }
        
        while(!q.empty()){
            int num = q.front();
            q.pop();
            for(auto i : graph[num]){
                inDegree[i]--;
                if(inDegree[i] == 0)
                    q.push(i);
            }
        }
        
        for(int i = 0;i < numCourses;i++){
            if(inDegree[i] != 0)
                return false;
        }
        return true;
    }
};