LeetCode | 74. Search a 2D Matrix

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 from left to right.
The first integer of each row is greater than the last integer of the previous row.

For example,

Consider the following matrix:

[
[1,   3,  5,  7],
[10, 11, 16, 20],
[23, 30, 34, 50]
]

Given target = 

3

, return 

true

.

题意：

在一个排序好的二维矩阵中，找到目标值target。算是剑指offer的一道经典题目。

代码：

bool searchMatrix(vector<vector<int>>& matrix, int target) {
int r = matrix.size(), c = r > 0 ? matrix[0].size() : 0;
int i = 0, j = c - 1;
while(i < r && j >= 0)
{
int cur = matrix[i][j];
if(cur == target)
return true;
if(cur < target)
i++;
else
j--;
}
return false;
}

时间复杂度最大是O(m+n)。