Unicity Distance Lite

Problem

Return the unicity distance: the amount of ciphertext needed on average to pin down the key. With key entropy in bits and per-character redundancy D:

U = key_bits / D

Assume the redundancy is positive.

Hint

Perfectly decodable ciphers have no redundancy and an infinite unicity distance.

case 1

in: [40,1.5]

expected: 26.666666666666668

case 2

in: [20,2]

expected: 10

case 3

in: [0,1.5]

expected: 0

case 4

in: [64,3]

expected: 21.333333333333332

Starter codePython

def unicity_distance(key_bits, redundancy_bits):
    # Your code here
    pass

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