Leetcode 207. Course Schedule

bool canFinish(int numCourses, vector<pair<int, int>>& prerequisites) {
    vector<vector<int>> matrix(numCourses,vector<int>(numCourses,0));
    vector<int> inDegree(numCourses);
    
    for(int i = 0;i < prerequisites.size();i++){
        int pre =  prerequisites[i].second;
        int ready = prerequisites[i].first;
        if(matrix[pre][ready] == 0){
            inDegree[ready]++;
            matrix[pre][ready] ++;
        }
    }
    
    int count = 0;
    queue<int> queue;
    for(int i = 0;i < inDegree.size();i++){
        if(inDegree[i] == 0){
            queue.push(i);
        }
    }
    
    while(!queue.empty()){
        int course = queue.front();
        queue.pop();
        count ++;
        for(int i = 0;i < numCourses;i++){
            if(matrix[course][i] != 0){
                if(--inDegree[i] == 0){
                    queue.push(i);
                }
            }
        }
    }
    return count == numCourses;
    
}