832. Flipping an Image

Question 832

https://leetcode.com/problems/flipping-an-image/ 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]]

Solution

row[~i] means row[-i-1]

v1

class Solution(object):
    def flipAndInvertImage(self, A):
        Ans = []
        for a in A:
            LEN = len(a)
            row = []
            for i in range(LEN):
                row.append( [1,0][a[LEN-1-i]] )
            Ans.append(row)
        return Ans

v2

class SolutionII(object):
    def flipAndInvertImage(self, A):
        for a in A:
            l,r = 0, len(a) - 1
            while l <= r:
                if a[l] == a[r]:
                    a[l],a[r] = a[l]^1, a[r]^1
                l += 1
                r -=1
        return A

v3

class SolutionIII(object):
    def flipAndInvertImage(self, A):

        for row in A:
            for i in range((len(row)+1) / 2):
                if( row[i] == row[~i] ):
                    row[i], row[~i] = row[~i]^1, row[i]^1
        return A