# nayuki/Project-Euler-solutions

Switch branches/tags
Nothing to show
Fetching contributors…
Cannot retrieve contributors at this time
44 lines (35 sloc) 988 Bytes
 # # Solution to Project Euler problem 41 # Copyright (c) Project Nayuki. All rights reserved. # # https://www.nayuki.io/page/project-euler-solutions # https://github.com/nayuki/Project-Euler-solutions # import eulerlib def compute(): # Note: The only 1-digit pandigital number is 1, which is not prime. Thus we require n >= 2. for n in reversed(range(2, 10)): arr = list(reversed(range(1, n + 1))) while True: if arr[-1] not in NONPRIME_LAST_DIGITS: n = int("".join(str(x) for x in arr)) if eulerlib.is_prime(n): return str(n) if not prev_permutation(arr): break raise AssertionError() NONPRIME_LAST_DIGITS = {0, 2, 4, 5, 6, 8} def prev_permutation(arr): i = len(arr) - 1 while i > 0 and arr[i - 1] <= arr[i]: i -= 1 if i <= 0: return False j = len(arr) - 1 while arr[j] >= arr[i - 1]: j -= 1 arr[i - 1], arr[j] = arr[j], arr[i - 1] arr[i : ] = arr[len(arr) - 1 : i - 1 : -1] return True if __name__ == "__main__": print(compute())