#74. Search a 2D Matrix

https://leetcode.com/problems/search-a-2d-matrix/#/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 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.

Python

class Solution(object):
    def searchMatrix(self, matrix, target):
        """
        :type matrix: List[List[int]]
        :type target: int
        :rtype: bool
        """
        # if not a: 是检查列表a是否为空最好的方法
        if not matrix or target is None:
            return False
        m = len(matrix)
        n = len(matrix[0])
        left = 0
        right = m * n - 1
        while left <= right:
            mid = left + (right - left) / 2
            t = matrix[mid / n][mid % n]
            if t == target:
                return True
            elif t > target:
                right = mid - 1
            else:
                left = mid + 1
        return False