304.cpp

//
//  304.cpp
//  leetcode
//
//  Created by R Z on 2018/1/16.
//  Copyright © 2018年 R Z. All rights reserved.
//

#include <stdio.h>
#include <vector>
using namespace std;
class NumMatrix {
private:
    int row, col;
    vector<vector<int>> sums;
public:
    NumMatrix(vector<vector<int>> matrix) {
        row = matrix.size();
        col = row>0?matrix[0].size():0;
        sums = vector<vector<int>>(row+1, vector<int>(col+1, 0));
        for(int i=1; i<=row;i++){
            for(int j=1; j<=col; j++){
                sums[i][j]=sums[i-1][j]+sums[i][j-1]-sums[i-1][j-1]+matrix[i-1][j-1];
            }
        }
    }
    
    int sumRegion(int row1, int col1, int row2, int col2) {
        return sums[row2+1][col2+1]-sums[row2+1][col1]-sums[row1][col2+1]+sums[row1][col1];
    }
};

/**
 * Your NumMatrix object will be instantiated and called as such:
 * NumMatrix obj = new NumMatrix(matrix);
 * int param_1 = obj.sumRegion(row1,col1,row2,col2);
 */