searchA2dMatrixII.js

/*
 * 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 || matrix.length === 0){ return false;}
    
    let numOfRows = matrix.length;
    let numOfCols = matrix[0].length;
    let colNum = numOfCols-1;    
    for(let rowNum=0;rowNum<numOfRows;rowNum++){
        while(colNum && matrix[rowNum][colNum] > target){
            colNum--;
        }
        
        if(matrix[rowNum][colNum] === target) {return true;}
    }
    
    return false;
};