[leetcode]Search a 2D Matrix @ Python

原题地址：https://oj.leetcode.com/problems/search-a-2d-matrix/

题意：

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.

解题思路：类似于二分查找。

代码：

class Solution:
    # @param matrix, a list of lists of integers
    # @param target, an integer
    # @return a boolean
    def searchMatrix(self, matrix, target):
        i = 0; j = len(matrix[0]) - 1
        while i < len(matrix) and j >= 0:
            if matrix[i][j] == target: return True
            elif matrix[i][j] > target: j -= 1
            else: i += 1
        return False