Online C++ Compiler

#include <bits/stdc++.h> using namespace std; class NumMatrix { public: vector < vector <int>> dp; NumMatrix(vector<vector<int>>& matrix) { int n = matrix.size(); if(!n) return; int m = matrix[0].size(); dp = vector < vector <int>>(n, vector <int> (m)); for(int i = 0; i < n; i++){ for(int j = 0 ;j < m; j++){ dp[i][j] = j - 1 < 0 ? matrix[i][j] : dp[i][j - 1] + matrix[i][j]; } } for(int i = 1; i < n; i++){ for(int j = 0; j < m; j++){ dp[i][j] += dp[i - 1][j]; } } } int sumRegion(int row1, int col1, int row2, int col2) { int ret = dp[row2][col2]; int sub1 = row1 - 1 < 0 ? 0 : dp[row1 - 1][col2]; int sub2 = col1 - 1 < 0 ? 0 : dp[row2][col1 - 1]; int add = row1 - 1 < 0 || col1 - 1 < 0 ? 0 : dp[row1 - 1][col1 - 1]; return ret - sub1 - sub2 + add; } }; main(){ vector<vector<int>> mat = {{3,0,1,4,2},{5,6,3,2,1},{1,2,0,1,5},{4,1,0,1,7},{1,0,3,0,5}}; NumMatrix ob(mat); cout << ob.sumRegion(2,1,4,3) << endl; cout << ob.sumRegion(1,1,2,2) << endl; cout << ob.sumRegion(1,2,2,4) << endl; }