Columnar Cipher Decrypt

Problem

Decrypt a columnar transposition cipher. The plaintext was written row by row into `columns` columns, then the columns were read in the order given by order, where order[read_index] is the column read at that position. The ciphertext length is divisible by columns. Return the plaintext string.

Hint

Split the ciphertext into chunks of one column height and place each chunk in the column it was read from.

Test cases

case 1

in: ["LRHWLLEOOD",5,[2,0,3,1,4]]

expected: "HELLOWORLD"

case 2

in: ["TKAATNACDTAW",4,[1,3,0,2]]

expected: "ATTACKATDAWN"

case 3

in: ["CFADBE",3,[2,0,1]]

expected: "ABCDEF"

Starter codePython

def columnar_decrypt(ciphertext, columns, order):
    # Your code here
    pass

3 test cases · run your code against them in the editor