queries on a martix.cpp

class Solution {
  public:
    vector<vector<int>> solveQueries(int n, vector<vector<int>> Queries) {
        vector<vector<int> > matrix(n,vector<int>(n,0));
        int q=Queries.size();
        for(int i=0;i<q;i++){
            int a,b,c,d;
            a=Queries[i][0];
            b=Queries[i][1];
            c=Queries[i][2];
            d=Queries[i][3];
            for(int j=a;j<=c;j++){
                matrix[j][b]+=1;
                if(d+1<n)
                 matrix[j][d+1]-=1;
            }
        }
        
        for(int i=0;i<n;i++){
            for(int j=1;j<n;j++){
                matrix[i][j]+=matrix[i][j-1];
            }
        }
        return matrix;
    }
};