描述

Given a binary matrix A, we want to flip the image horizontally, then invert it, and return the resulting image.

To flip an image horizontally means that each row of the image is reversed. For example, flipping [1, 1, 0] horizontally results in [0, 1, 1].

To invert an image means that each 0 is replaced by 1, and each 1 is replaced by 0. For example, inverting [0, 1, 1] results in [1, 0, 0].

Example 1:

Input: [[1,1,0],[1,0,1],[0,0,0]]
Output: [[1,0,0],[0,1,0],[1,1,1]]
Explanation: First reverse each row: [[0,1,1],[1,0,1],[0,0,0]].
Then, invert the image: [[1,0,0],[0,1,0],[1,1,1]]

Example 2:

Input: [[1,1,0,0],[1,0,0,1],[0,1,1,1],[1,0,1,0]]
Output: [[1,1,0,0],[0,1,1,0],[0,0,0,1],[1,0,1,0]]
Explanation: First reverse each row: [[0,0,1,1],[1,0,0,1],[1,1,1,0],[0,1,0,1]].
Then invert the image: [[1,1,0,0],[0,1,1,0],[0,0,0,1],[1,0,1,0]]

Notes:

1 <= A.length = A[0].length <= 20
0 <= A[i][j] <= 1

解析

这里的题意比较简单，如果是常规做法可能代码很繁琐，在本解答算法中主要用到了 Python 中的一些 list 索引的使用小技巧，还有位运算的小知识点。

解答

class Solution(object):
def flipAndInvertImage(self, A):
    """
    :type A: List[List[int]]
    :rtype: List[List[int]]
    """
    for row in A:
        for i in range((len(row)+1)/2):
            row[i], row[~i] = row[~i]^1, row[i]^1
    return A

运行结果

Runtime: 36 ms, faster than 81.20% of Python online submissions for Squares of a Sorted Array.
Memory Usage: 11.7 MB, less than 55.29% of Python online submissions for Squares of a Sorted Array.

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