Python/maths/binary_exp_mod.py
Anzo Teh 725834b9bc Added binary exponentiaion with respect to modulo (#1428)
* Added binary exponentiaion with respect to modulo

* Added miller rabin: the probabilistic primality test for large numbers

* Removed unused import

* Added test for miller_rabin

* Add test to binary_exp_mod

* Removed test parameter to make Travis CI happy

* unittest.main()  # doctest: +ELLIPSIS   ...

* Update binary_exp_mod.py

* Update binary_exp_mod.py

* Update miller_rabin.py

* from .prime_check import prime_check

Co-authored-by: Christian Clauss <cclauss@me.com>
2019-12-24 07:23:15 +01:00

29 lines
661 B
Python

def bin_exp_mod(a, n, b):
"""
>>> bin_exp_mod(3, 4, 5)
1
>>> bin_exp_mod(7, 13, 10)
7
"""
# mod b
assert not (b == 0), "This cannot accept modulo that is == 0"
if n == 0:
return 1
if n % 2 == 1:
return (bin_exp_mod(a, n - 1, b) * a) % b
r = bin_exp_mod(a, n / 2, b)
return (r * r) % b
if __name__ == "__main__":
try:
BASE = int(input("Enter Base : ").strip())
POWER = int(input("Enter Power : ").strip())
MODULO = int(input("Enter Modulo : ").strip())
except ValueError:
print("Invalid literal for integer")
print(bin_exp_mod(BASE, POWER, MODULO))