/**
 * https://leetcode.com/problems/range-sum-query-2d-immutable/
 * @class NumMatrix
 * @param {number[][]} matrix
 */
class NumMatrix {
    constructor(matrix) {
        this.matrix = matrix;
    }

    /**
     *
     * m = row2 - row1; n = col2 - col1
     * Time O(m*n) | Space O(1)
     * @param {number} row1
     * @param {number} col1
     * @param {number} row2
     * @param {number} col2
     * @return {number}
     */
    sumRegion(row1, col1, row2, col2) {
        let sum = 0;
        for (let i = row1; i < row2 + 1; i++) {
            for (let j = col1; j < col2 + 1; j++) {
                sum += this.matrix[i][j];
            }
        }
        return sum;
    }
}

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