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Arun Kishore Voletipre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>Christian Clauss* Add is_even_using_shift_operator function Introduces a new function to check if a number is even using bitwise shift operators. Includes docstring with explanation and doctest examples. * [pre-commit.ci] auto fixes from pre-commit.com hooks for more information, see https://pre-commit.ci --------- Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com> Co-authored-by: Christian Clauss <cclauss@me.com>
76 lines
1.8 KiB
Python
76 lines
1.8 KiB
Python
def is_even(number: int) -> bool:
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"""Return True if the input integer is even using a bitwise check.
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Explanation:
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In binary, even numbers always have the least significant bit cleared (0),
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while odd numbers have it set (1). Therefore, ``n & 1 == 0`` implies even.
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>>> is_even(1)
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False
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>>> is_even(4)
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True
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>>> is_even(9)
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False
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>>> is_even(15)
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False
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>>> is_even(40)
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True
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>>> is_even(100)
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True
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>>> is_even(101)
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False
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>>> is_even(True)
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Traceback (most recent call last):
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...
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TypeError: input must be an integer
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>>> is_even(3.14)
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Traceback (most recent call last):
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...
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TypeError: input must be an integer
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"""
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if not isinstance(number, int) or isinstance(number, bool):
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# bool is a subclass of int; explicitly disallow it as a number here.
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raise TypeError("input must be an integer")
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return (number & 1) == 0
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def is_even_using_shift_operator(number: int) -> bool:
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"""
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Returns True if the input integer is even.
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Explanation:
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In binary, even numbers end with 0, odd numbers end with 1.
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Examples:
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2 -> 10
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3 -> 11
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4 -> 100
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5 -> 101
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For odd numbers, the last bit is always 1.
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Using shift:
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(n >> 1) << 1 removes the last bit.
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If result equals n, n is even.
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>>> is_even_using_shift_operator(1)
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False
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>>> is_even_using_shift_operator(4)
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True
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>>> is_even_using_shift_operator(9)
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False
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>>> is_even_using_shift_operator(15)
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False
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>>> is_even_using_shift_operator(40)
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True
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>>> is_even_using_shift_operator(100)
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True
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>>> is_even_using_shift_operator(101)
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False
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"""
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return (number >> 1) << 1 == number
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if __name__ == "__main__":
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import doctest
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doctest.testmod()
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