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Power using recursion: correctly implemented recursion #5050

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Power using recursion: correctly implemented recursion #5050

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a2c93f0
fix: integer power should return int not float
matssson Oct 5, 2021
4137cf7
fix: recursion wasnt implemented correctly, and now we throw a valuee…
matssson Oct 5, 2021
f31e711
Remove valueError for 0^0
matssson Oct 5, 2021
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13 changes: 10 additions & 3 deletions maths/power_using_recursion.py
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Original file line number Diff line number Diff line change
Expand Up @@ -13,7 +13,7 @@
"""


def power(base: int, exponent: int) -> float:
def power(base: int, exponent: int) -> int:
"""
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Please add a test for 0^0?

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But I removed the check for 0^0 since the testing suite expected it to return 1, which math.pow does

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@poyea poyea Oct 6, 2021 •
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You may reference those fast exp in the same folder and see what are their behaviour. It's still ok to add tests for this function.

power(3, 4)
81
Expand All @@ -23,7 +23,14 @@ def power(base: int, exponent: int) -> float:
... for base in range(-10, 10) for exponent in range(10))
True
"""
return base * power(base, (exponent - 1)) if exponent else 1
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I think this works for 0^0.

if exponent == 0:
return 1
if exponent == 1:
return base
if exponent % 2 == 0:
return power(base * base, exponent // 2)
else:
return base * power(base * base, (exponent - 1) // 2)


if __name__ == "__main__":
Expand All @@ -32,5 +39,5 @@ def power(base: int, exponent: int) -> float:
exponent = int(input("Enter the exponent: ").strip())
result = power(base, abs(exponent))
if exponent < 0: # power() does not properly deal w/ negative exponents
result = 1 / result
result = 1.0 / result
print(f"{base} to the power of {exponent} is {result}")