mirror of
https://github.com/TheAlgorithms/Python.git
synced 2024-11-24 13:31:07 +00:00
45 lines
874 B
Python
45 lines
874 B
Python
"""
|
|
Modular Exponential.
|
|
Modular exponentiation is a type of exponentiation performed over a modulus.
|
|
For more explanation, please check https://en.wikipedia.org/wiki/Modular_exponentiation
|
|
"""
|
|
|
|
"""Calculate Modular Exponential."""
|
|
|
|
|
|
def modular_exponential(base: int, power: int, mod: int):
|
|
"""
|
|
>>> modular_exponential(5, 0, 10)
|
|
1
|
|
>>> modular_exponential(2, 8, 7)
|
|
4
|
|
>>> modular_exponential(3, -2, 9)
|
|
-1
|
|
"""
|
|
|
|
if power < 0:
|
|
return -1
|
|
base %= mod
|
|
result = 1
|
|
|
|
while power > 0:
|
|
if power & 1:
|
|
result = (result * base) % mod
|
|
power = power >> 1
|
|
base = (base * base) % mod
|
|
|
|
return result
|
|
|
|
|
|
def main():
|
|
"""Call Modular Exponential Function."""
|
|
print(modular_exponential(3, 200, 13))
|
|
|
|
|
|
if __name__ == "__main__":
|
|
import doctest
|
|
|
|
doctest.testmod()
|
|
|
|
main()
|