LeetCode Q74: Search a 2D Matrix

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.

Solution 1:
Binary search, but at the end, you need to search two rows before making a decision. Time complexity O(logm + logn).

Solution 2:
Start from up right corner, if larger than move down, if smaller than move left. Time complexity O(m+n)