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49 lines
1.0 KiB
Python
49 lines
1.0 KiB
Python
"""Binary Exponentiation."""
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# Author : Junth Basnet
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# Time Complexity : O(logn)
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def binary_exponentiation(a: int, n: int) -> int:
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"""
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Compute a number raised by some quantity
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>>> binary_exponentiation(-1, 3)
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-1
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>>> binary_exponentiation(-1, 4)
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1
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>>> binary_exponentiation(2, 2)
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4
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>>> binary_exponentiation(3, 5)
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243
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>>> binary_exponentiation(10, 3)
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1000
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>>> binary_exponentiation(5e3, 1)
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5000.0
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>>> binary_exponentiation(-5e3, 1)
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-5000.0
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"""
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if n == 0:
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return 1
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elif n % 2 == 1:
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return binary_exponentiation(a, n - 1) * a
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else:
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b = binary_exponentiation(a, n // 2)
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return b * b
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if __name__ == "__main__":
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import doctest
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doctest.testmod()
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try:
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BASE = int(float(input("Enter Base : ").strip()))
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POWER = int(input("Enter Power : ").strip())
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except ValueError:
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print("Invalid literal for integer")
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RESULT = binary_exponentiation(BASE, POWER)
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print(f"{BASE}^({POWER}) : {RESULT}")
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