SANS Holiday Hack 2019 Dormitory Keypad Solver

dorm_pad.py

# SANS Holiday Hack 2019 Dormitory Keypad Solver

from itertools import product

# https://stackoverflow.com/questions/46841968/fastest-way-of-testing-if-a-number-is-prime-with-python
def is_prime(n):
    if n & 1 == 0:
        return False
    d= 3
    while d * d <= n:
        if n % d == 0:
            return False
        d= d + 2
    return True


digits = [1, 3, 7]
for opt in product(digits, repeat=4):
    if set(digits).issubset(opt):  # Must contain all digits at least once
        opt = int(''.join(str(c) for c in opt))
        if is_prime(opt):
            print(opt)

Output:

1373
1733
3137
3371
7331

Solution was 7331 AKA 1337 backwards, because of course it is.