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110 lines
3.3 KiB
Python
110 lines
3.3 KiB
Python
# Information on binary shifts:
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# https://docs.python.org/3/library/stdtypes.html#bitwise-operations-on-integer-types
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# https://www.interviewcake.com/concept/java/bit-shift
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def logical_left_shift(number: int, shift_amount: int) -> str:
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"""
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Take in 2 positive integers.
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'number' is the integer to be logically left shifted 'shift_amount' times.
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i.e. (number << shift_amount)
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Return the shifted binary representation.
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>>> logical_left_shift(0, 1)
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'0b00'
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>>> logical_left_shift(1, 1)
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'0b10'
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>>> logical_left_shift(1, 5)
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'0b100000'
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>>> logical_left_shift(17, 2)
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'0b1000100'
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>>> logical_left_shift(1983, 4)
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'0b111101111110000'
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>>> logical_left_shift(1, -1)
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Traceback (most recent call last):
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...
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ValueError: both inputs must be positive integers
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"""
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if number < 0 or shift_amount < 0:
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raise ValueError("both inputs must be positive integers")
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binary_number = str(bin(number))
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binary_number += "0" * shift_amount
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return binary_number
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def logical_right_shift(number: int, shift_amount: int) -> str:
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"""
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Take in positive 2 integers.
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'number' is the integer to be logically right shifted 'shift_amount' times.
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i.e. (number >>> shift_amount)
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Return the shifted binary representation.
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>>> logical_right_shift(0, 1)
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'0b0'
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>>> logical_right_shift(1, 1)
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'0b0'
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>>> logical_right_shift(1, 5)
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'0b0'
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>>> logical_right_shift(17, 2)
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'0b100'
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>>> logical_right_shift(1983, 4)
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'0b1111011'
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>>> logical_right_shift(1, -1)
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Traceback (most recent call last):
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...
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ValueError: both inputs must be positive integers
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"""
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if number < 0 or shift_amount < 0:
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raise ValueError("both inputs must be positive integers")
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binary_number = str(bin(number))[2:]
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if shift_amount >= len(binary_number):
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return "0b0"
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shifted_binary_number = binary_number[: len(binary_number) - shift_amount]
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return "0b" + shifted_binary_number
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def arithmetic_right_shift(number: int, shift_amount: int) -> str:
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"""
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Take in 2 integers.
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'number' is the integer to be arithmetically right shifted 'shift_amount' times.
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i.e. (number >> shift_amount)
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Return the shifted binary representation.
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>>> arithmetic_right_shift(0, 1)
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'0b00'
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>>> arithmetic_right_shift(1, 1)
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'0b00'
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>>> arithmetic_right_shift(-1, 1)
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'0b11'
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>>> arithmetic_right_shift(17, 2)
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'0b000100'
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>>> arithmetic_right_shift(-17, 2)
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'0b111011'
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>>> arithmetic_right_shift(-1983, 4)
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'0b111110000100'
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"""
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if number >= 0: # Get binary representation of positive number
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binary_number = "0" + str(bin(number)).strip("-")[2:]
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else: # Get binary (2's complement) representation of negative number
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binary_number_length = len(bin(number)[3:]) # Find 2's complement of number
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binary_number = bin(abs(number) - (1 << binary_number_length))[3:]
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binary_number = (
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"1" + "0" * (binary_number_length - len(binary_number)) + binary_number
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)
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if shift_amount >= len(binary_number):
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return "0b" + binary_number[0] * len(binary_number)
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return (
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"0b"
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+ binary_number[0] * shift_amount
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+ binary_number[: len(binary_number) - shift_amount]
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)
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if __name__ == "__main__":
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import doctest
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doctest.testmod()
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