Flipping a matrix-like string horizontally-CodePudding

The goal of this function is to flip a matrix-like string horizontally.

for example the string: '100010001' with 2 rows and three columns would look like:

1 0 0

0 1 0

0 0 1

but when flipped should look like:

0 0 1

0 1 0

1 0 0

so the function would return the following output: '001010100'

The caveat, I cannot use lists or arrays. only strings.

The current code I have written up, I believe, should work, however it is returning an empty string.

def flip_horizontal(image, rows, column):

   horizontal_image = ''
   for i in range(rows):

       #This should slice the image string, and map image(the last element in the 
       #coloumn : to the first element of the column) onto horizontal_image.
       #this will repeat for the given amount of rows

       horizontal_image = horizontal_image   image[(i 1)*column-1:i*column]
    
   return horizontal_image

again this returns an empty string. Any clue what is the issue?

CodePudding user response：

Use [::-1] to reverse each row of the image.

def flip(im, w):
    return ''.join(im[i:i w][::-1] for i in range(0, len(im), w))

>>> im = '100010001'
>>> flip(im, 3)
'001010100'

CodePudding user response：

The range function can be used to isolate your string into steps that represent rows. While iterating through the string you can use [::-1] to reverse each row to achieve the horizontal flip.

string = '100010001'
output = ''
prev = 0

# Iterate through string in steps of 3
for i in range(3, len(string)   1, 3):

  # Isolate and reverse row of string
  row = string[prev:i]
  row = row[::-1]

  output = output   row
  prev = i

Input:

'100
 010
 001'

Output:

'001
 010
 100'