Code is taking too much time

Question

I wrote code to arrange numbers after taking user input. The ordering requires that the sum of adjacent numbers is prime. Up until 10 as an input code is working fine. If I

Answer 1

Dynamic programming, to the rescue:

def is_prime(n):
    return all(n % i != 0 for i in range(2, n))

def order(numbers, current=[]):
    if not numbers:
        return current

    for i, n in enumerate(numbers):
        if current and not is_prime(n + current[-1]):
            continue

        result = order(numbers[:i] + numbers[i + 1:], current + [n])

        if result:
            return result

    return False

result = order(range(500))

for i in range(len(result) - 1):
    assert is_prime(result[i] + result[i + 1])

You can force it to work for even larger lists by increasing the maximum recursion depth.