Affine Key Valid

Problem

Return True when the affine multiplier a is invertible modulo 26, that is, when gcd(a, 26) = 1. Otherwise the cipher is not a bijection and cannot be decrypted uniquely.

Hint

The valid multipliers are coprime to 26, so even and 13-multiples fail.

Test cases

case 1

in: [1]

expected: true

case 2

in: [3]

expected: true

case 3

in: [2]

expected: false

case 4

in: [13]

expected: false

case 5

in: [25]

expected: true

Starter codePython

import math
def affine_key_valid(a):
    # Your code here
    pass

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