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Unify O(sqrt(N)) is_prime functions under project_euler (#6258)

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* fixes #5434

* fixes broken solution

* removes assert

* removes assert

* Apply suggestions from code review

Co-authored-by: John Law <johnlaw.po@gmail.com>

* Update project_euler/problem_003/sol1.py

Co-authored-by: John Law <johnlaw.po@gmail.com>
This commit is contained in:
Nikos Giachoudis
2022-09-14 11:40:04 +03:00
committed by GitHub
parent 81e30fd33c
commit 2104fa7aeb
12 changed files with 313 additions and 135 deletions
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30
project_euler/problem_003/sol1.py
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@ -13,9 +13,11 @@ References:
import math
def is_prime(num: int) -> bool:
"""
Returns boolean representing primality of given number num.
def is_prime(number: int) -> bool:
"""Checks to see if a number is a prime in O(sqrt(n)).
A number is prime if it has exactly two factors: 1 and itself.
Returns boolean representing primality of given number (i.e., if the
result is true, then the number is indeed prime else it is not).
>>> is_prime(2)
True
@ -26,23 +28,21 @@ def is_prime(num: int) -> bool:
>>> is_prime(2999)
True
>>> is_prime(0)
Traceback (most recent call last):
...
ValueError: Parameter num must be greater than or equal to two.
False
>>> is_prime(1)
Traceback (most recent call last):
...
ValueError: Parameter num must be greater than or equal to two.
False
"""
if num <= 1:
raise ValueError("Parameter num must be greater than or equal to two.")
if num == 2:
if 1 < number < 4:
# 2 and 3 are primes
return True
elif num % 2 == 0:
elif number < 2 or number % 2 == 0 or number % 3 == 0:
# Negatives, 0, 1, all even numbers, all multiples of 3 are not primes
return False
for i in range(3, int(math.sqrt(num)) + 1, 2):
if num % i == 0:
# All primes number are in format of 6k +/- 1
for i in range(5, int(math.sqrt(number) + 1), 6):
if number % i == 0 or number % (i + 2) == 0:
return False
return True