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24 changes: 15 additions & 9 deletions src/math/number_theory.py
Original file line number Diff line number Diff line change
Expand Up @@ -4,22 +4,28 @@

def gcd_recursive(a: int, b: int) -> int:
"""Calculate greatest common divisor using Euclidean algorithm with recursion."""
if b == 0:
return a
return gcd_recursive(b, a % b)
while b != 0:
a, b = b, a % b
return a


def sieve_of_eratosthenes(n: int) -> List[int]:
"""Find all primes up to n using sieve of Eratosthenes."""
if n <= 1:
return []

is_prime = [True] * (n + 1)
is_prime[0] = is_prime[1] = False
is_prime = bytearray(b"\x01") * (n + 1)
is_prime[0] = is_prime[1] = 0

for i in range(2, int(math.sqrt(n)) + 1):
if n >= 4:
is_prime[4 : n + 1 : 2] = b"\x00" * (((n - 4) // 2) + 1)

for i in range(3, math.isqrt(n) + 1, 2):
if is_prime[i]:
for j in range(i * i, n + 1, i):
is_prime[j] = False
start = i * i
step = i * 2
is_prime[start : n + 1 : step] = b"\x00" * ((n - start) // step + 1)

return [i for i in range(2, n + 1) if is_prime[i]]
primes = [2] if n >= 2 else []
primes.extend(i for i in range(3, n + 1, 2) if is_prime[i])
return primes
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