Search a 2D Matrix II

题目来源LeetCode

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.

这道题从矩阵的右上角开始，根据行列都是从小到大排列的性质，目标小于矩阵数则列数-1，目标大于矩阵数则行数+1，（这道题遇到的问题是没有考虑矩阵为空，需要判断一下再进行）代码如下：

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