Search_a_2D_Matrix_II.js

/*
Search a 2D Matrix II
https://leetcode.com/problems/search-a-2d-matrix-ii/description/

Write an efficient algorithm that searches for a value in an m x n matrix. This matrix has the following properties:
Integers in each row are sorted in ascending from left to right.
Integers in each column are sorted in ascending from top to bottom.
Example:
 Consider the following matrix:
 [
  [1,   4,  7, 11, 15],
  [2,   5,  8, 12, 19],
  [3,   6,  9, 16, 22],
  [10, 13, 14, 17, 24],
  [18, 21, 23, 26, 30]
]
Given target = 5, return true.
Given target = 20, return false.
*/

/**
 * @param {number[][]} matrix
 * @param {number} target
 * @return {boolean}
 */
var searchMatrix = function (matrix, target) {
  if (matrix.length == 0) return false;
  var lastCol = matrix[0].length - 1;
  var firstRow = 0;

  while (lastCol >= 0 && firstRow < matrix.length) {
    if (matrix[firstRow][lastCol] == target) {
      return true;
    } else if (matrix[firstRow][lastCol] > target) {
      lastCol--;
    } else {
      firstRow++;
    }
  }

  return false;
};

module.exports.searchMatrix = searchMatrix;