240. Search a 2D Matrix II

题目：

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.

解题思路：

没感觉和Search a 2D Matrix有什么区别，先将上一份代码复制过来，依然通过。那就这样吧~~

class Solution {public:    bool searchMatrix(vector<vector<int>>& matrix, int target) {        if(matrix.size()==0)return false;        int rows = matrix.size(), columns = matrix[0].size();        int row=0, column=columns-1;        while(row<rows && column>=0)        {            if(matrix[row][column]==target)return true;            if(matrix[row][column]>target)column--;            else                row++;        }        return false;            }};