117 lines
2.5 KiB
Python
117 lines
2.5 KiB
Python
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# Problem 3:
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#
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# A palindromic number reads the same both ways.
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# The largest palindrome made from the product
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# of two 2-digit numbers is 9009 = 91 × 99.
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#
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# Find the largest palindrome made from the
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# product of two 3-digit numbers.
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#
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import decorators
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import time
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# Create function that finds the next
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# prime number when supplied with an
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# intitial integer.
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def is_palindrome(candidate):
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"""
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Returns a boolean to confirm if the passed
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integer is a palindrome.
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is_palindrome(candidate)
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param 'candidate': Integer to test for palindrom-iness.
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"""
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# Convert maximum candidate to a list ...
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listed_candidate = [int(i) for i in str(candidate)]
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flipped_candidate = [int(i) for i in str(candidate)]
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#print("{}".format(listed_candidate))
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# Determine length of maximum candidate, and manipulate.
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num_digits = listed_candidate.__len__()
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digit_flips = int(num_digits/2)
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for i in range(1,digit_flips):
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#print("{}".format(i))
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flipped_candidate[-i-1] = flipped_candidate[i]
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flipped_candidate[-1] = flipped_candidate[0]
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#print("{}".format(flipped_candidate))
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# Compare ...
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if listed_candidate == flipped_candidate:
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return True
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else:
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return False
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@decorators.function_timer
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def main():
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# Define the problem inputs...
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factor_length = 3
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# Calculate intermediate inputs...
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max_factor = 10**(factor_length)-1
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product_of_factors = max_factor * max_factor # Maximum candidate for palindrome test.
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# Initialize loop parameters...
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n = max_factor
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m = max_factor
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n_has_token = False
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test_passed = False
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palindrome_list=[]
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while (n*m)>0:
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# Test for "palindrom-iness" ...
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print("{} * {} = {}".format(n,m,n*m))
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test_passed = is_palindrome(n*m)
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# if not test_passed and n_has_token:
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# n -= 1
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# if n == 1:
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# n_has_token = False
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# n = max_factor
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# elif not test_passed and not n_has_token:
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# m -= 1
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# n_has_token = True
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# else:
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# palindrome_list.append(n*m)
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#
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if test_passed:
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palindrome_list.append(n*m)
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if n_has_token:
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n -= 1
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if n ==1:
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n_has_token = False
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n = max_factor
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if not n_has_token:
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m -= 1
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n_has_token = True
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if not test_passed:
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if n_has_token:
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n -= 1
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if n ==1:
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n_has_token = False
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n = max_factor
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if not n_has_token:
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m -= 1
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n_has_token = True
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print("{}".format(max(palindrome_list)))
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# print("{} * {} = {}".format(n,m,n*m))
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# print("The largest palindrome number which is a product of two numbers of length {} is {} ... ".format(num_digits,num_digits))
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main() |