[LeetCode][JavaScript]Search a 2D Matrix II

Search a 2D Matrix II

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.

For 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.

https://leetcode.com/problems/search-a-2d-matrix-ii/

从右上角开始，如果当前的数大于target，列号减一(左移一列)，如果当前的数小于target，行号加一(下移一行)。

从左下角开始找也是一样的。

 1 /**
 2  * @param {number[][]} matrix
 3  * @param {number} target
 4  * @return {boolean}
 5  */
 6 var searchMatrix = function(matrix, target) {
 7     return findTarget(0, matrix[0].length - 1);
 8
 9     function findTarget(i, j){
10         if(matrix[i][j] === target){
11             return true;
12         }
13         if(matrix[i][j] > target){
14             if(!matrix[i][j - 1]){
15                 return false;
16             }else{
17                 return findTarget(i, j - 1);
18             }
19         }
20         if(matrix[i][j] < target){
21             if(!matrix[i + 1]){
22                 return false;
23             }else{
24                 return findTarget(i + 1, j);
25             }
26         }
27     }
28 };