TheAlgorithms-Python

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"""
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Problem 28
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Url: https://projecteuler.net/problem=28
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Statement:
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Starting with the number 1 and moving to the right in a clockwise direction a 5
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by 5 spiral is formed as follows:
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    21 22 23 24 25
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    20  7  8  9 10
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    19  6  1  2 11
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    18  5  4  3 12
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    17 16 15 14 13
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It can be verified that the sum of the numbers on the diagonals is 101.
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What is the sum of the numbers on the diagonals in a 1001 by 1001 spiral formed
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in the same way?
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"""
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from math import ceil
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def solution(n: int = 1001) -> int:
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    """Returns the sum of the numbers on the diagonals in a n by n spiral
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    formed in the same way.
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    >>> solution(1001)
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    669171001
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    >>> solution(500)
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    82959497
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    >>> solution(100)
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    651897
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    >>> solution(50)
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    79697
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    >>> solution(10)
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    537
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    """
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    total = 1
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    for i in range(1, int(ceil(n / 2.0))):
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        odd = 2 * i + 1
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        even = 2 * i
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        total = total + 4 * odd**2 - 6 * even
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    return total
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if __name__ == "__main__":
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    import sys
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    if len(sys.argv) == 1:
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        print(solution())
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    else:
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        try:
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            n = int(sys.argv[1])
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            print(solution(n))
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        except ValueError:
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            print("Invalid entry - please enter a number")
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