def product_pandigital(a,b):
c = a * b
digits = [int(x) for x in list(str(a)) + list(str(b)) + list(str(c))]
digits = int(''.join(map(str, digits)))
if is_pandigital(digits, 9):
return True
return False
def solve():
guess = 50000 # definite maximum
while True:
check_this = int(str(guess) + str(2 * guess)) # base case
n = 3
while check_this <= 987654321:
if is_pandigital(check_this, 9):
return check_this
check_this = int(str(check_this) + str(n * guess))
n += 1
guess -= 1
def solve():
best_case = '987654321' # 9 digit pandigital would be ideal
while best_case != '':
guess_perms = sorted([int(''.join(p)) for p in permutations(best_case)], reverse = True) # find all pandigitals
for guess in guess_perms:
if is_pandigital(guess, len(best_case)) and is_prime(guess):
return guess
else:
guess -= 1
best_case = best_case[1:] # truncate if we give up on this many digits
