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17 lines
447 B
Python
17 lines
447 B
Python
def gcd(a: int, b: int) -> int:
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while a != 0:
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a, b = b % a, a
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return b
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def find_mod_inverse(a: int, m: int) -> int:
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if gcd(a, m) != 1:
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msg = f"mod inverse of {a!r} and {m!r} does not exist"
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raise ValueError(msg)
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u1, u2, u3 = 1, 0, a
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v1, v2, v3 = 0, 1, m
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while v3 != 0:
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q = u3 // v3
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v1, v2, v3, u1, u2, u3 = (u1 - q * v1), (u2 - q * v2), (u3 - q * v3), v1, v2, v3
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return u1 % m
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