304. Range Sum Query 2D

class NumMatrix {public:    vector<vector<int>> *sums;    NumMatrix(vector<vector<int>> matrix) {        if(0 == matrix.size())            return;        sums = new vector<vector<int>>(matrix.size(), vector<int>(matrix[0].size(), 0));        (*sums)[0][0] = matrix[0][0];        for(int col = 1; col < matrix[0].size(); ++col){            (*sums)[0][col] = matrix[0][col] + (*sums)[0][col-1];        }        for(int row = 1; row < matrix.size(); ++row){            (*sums)[row][0] = matrix[row][0] + (*sums)[row-1][0];            int csum = matrix[row][0];            for(int col = 1; col < matrix[0].size(); ++col){                csum+=matrix[row][col];                (*sums)[row][col] = csum + (*sums)[row-1][col];            }        }    }        int sumRegion(int row1, int col1, int row2, int col2) {        return (*sums)[row2][col2] - ((col1==0)?0:(*sums)[row2][col1-1]) - ((row1==0)?0:(*sums)[row1-1][col2]) + ((col1==0||row1==0)?0:(*sums)[row1-1][col1-1]);    }};