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267b5eff40
* Added doctest and more explanation about Dijkstra execution. * tests were not passing with python2 due to missing __init__.py file at number_theory folder * Removed the dot at the beginning of the imported modules names because 'python3 -m doctest -v data_structures/hashing/*.py' and 'python3 -m doctest -v data_structures/stacks/*.py' were failing not finding hash_table.py and stack.py modules. * Moved global code to main scope and added doctest for project euler problems 1 to 14. * Added test case for negative input. * Changed N variable to do not use end of line scape because in case there is a space after it the script will break making it much more error prone. * Added problems description and doctests to the ones that were missing. Limited line length to 79 and executed python black over all scripts. * Changed the way files are loaded to support pytest call. * Added __init__.py to problems to make them modules and allow pytest execution. * Added project_euler folder to test units execution * Changed 'os.path.split(os.path.realpath(__file__))' to 'os.path.dirname()'
51 lines
1.3 KiB
Python
51 lines
1.3 KiB
Python
"""
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Problem:
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A palindromic number reads the same both ways. The largest palindrome made from
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the product of two 2-digit numbers is 9009 = 91 x 99.
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Find the largest palindrome made from the product of two 3-digit numbers which
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is less than N.
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"""
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from __future__ import print_function
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try:
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raw_input # Python 2
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except NameError:
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raw_input = input # Python 3
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def solution(n):
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"""Returns the largest palindrome made from the product of two 3-digit
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numbers which is less than n.
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>>> solution(20000)
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19591
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>>> solution(30000)
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29992
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>>> solution(40000)
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39893
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"""
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# fetchs the next number
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for number in range(n - 1, 10000, -1):
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# converts number into string.
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strNumber = str(number)
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# checks whether 'strNumber' is a palindrome.
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if strNumber == strNumber[::-1]:
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divisor = 999
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# if 'number' is a product of two 3-digit numbers
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# then number is the answer otherwise fetch next number.
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while divisor != 99:
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if (number % divisor == 0) and (
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len(str(int(number / divisor))) == 3
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):
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return number
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divisor -= 1
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if __name__ == "__main__":
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print(solution(int(raw_input().strip())))
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