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.

问题描述：

搜索二维矩阵I的变体，矩阵中每行元素递增，每列元素也是递增的。在矩阵中寻找目标元素。。。

解法一：

思路：

我们知道左上角一定是最小元素，右下角一定是最大元素。。由此可以从左下角元素与目标元素比较，
如果target > 则去掉这列
如果target < 则去掉这行

Code:

public class Solution {    public boolean searchMatrix(int[][] matrix, int target) {        if (matrix == null || matrix.length == 0){            return false;        }        if (matrix[0] == null || matrix[0].length ==0){            return false;        }        int row = matrix.length;        int col = matrix[0].length;        int x = row - 1;        int y = 0;        while (x >= 0 && y < col){            if (target == matrix[x][y]){                return true;            }            else if (target > matrix[x][y]){                y++;            }            else if (target < matrix[x][y]){                x--;            }        }        return false;    }}