From 66d26a1ad3cf2aecd9aa7c6f5565aaed02ca1bc3 Mon Sep 17 00:00:00 2001
From: Matsson <contact@matsson.org>
Date: Tue, 5 Oct 2021 18:37:27 +0200
Subject: [PATCH 1/2] Remove duplicate algorithm, other one is older, more
 sensibly named and better implemented.

---
 maths/prime_sieve_eratosthenes.py | 47 -------------------------------
 1 file changed, 47 deletions(-)
 delete mode 100644 maths/prime_sieve_eratosthenes.py

diff --git a/maths/prime_sieve_eratosthenes.py b/maths/prime_sieve_eratosthenes.py
deleted file mode 100644
index 8d60e48c2140..000000000000
--- a/maths/prime_sieve_eratosthenes.py
+++ /dev/null
@@ -1,47 +0,0 @@
-# flake8: noqa
-
-"""
-Sieve of Eratosthenes
-
-Input : n =10
-Output: 2 3 5 7
-
-Input : n = 20
-Output: 2 3 5 7 11 13 17 19
-
-you can read in detail about this at
-https://en.wikipedia.org/wiki/Sieve_of_Eratosthenes
-"""
-
-
-def prime_sieve_eratosthenes(num):
-    """
-    print the prime numbers up to n
-
-    >>> prime_sieve_eratosthenes(10)
-    2,3,5,7,
-    >>> prime_sieve_eratosthenes(20)
-    2,3,5,7,11,13,17,19,
-    """
-
-    primes = [True for i in range(num + 1)]
-    p = 2
-
-    while p * p <= num:
-        if primes[p]:
-            for i in range(p * p, num + 1, p):
-                primes[i] = False
-        p += 1
-
-    for prime in range(2, num + 1):
-        if primes[prime]:
-            print(prime, end=",")
-
-
-if __name__ == "__main__":
-    import doctest
-
-    doctest.testmod()
-    num = int(input())
-
-    prime_sieve_eratosthenes(num)

From f8a911679e276e6c42f31c296d6715872a2beb18 Mon Sep 17 00:00:00 2001
From: Matsson <contact@matsson.org>
Date: Tue, 5 Oct 2021 19:09:17 +0200
Subject: [PATCH 2/2] Iterate by 2 instead of 1, remove dependencies and
 simplify names

---
 maths/sieve_of_eratosthenes.py | 43 +++++++++++++++++-----------------
 1 file changed, 21 insertions(+), 22 deletions(-)

diff --git a/maths/sieve_of_eratosthenes.py b/maths/sieve_of_eratosthenes.py
index 3cd6ce0b4d9d..be0a5d4fc629 100644
--- a/maths/sieve_of_eratosthenes.py
+++ b/maths/sieve_of_eratosthenes.py
@@ -10,9 +10,6 @@
 doctest provider: Bruno Simas Hadlich (https://github.com/brunohadlich)
 Also thanks to Dmitry (https://github.com/LizardWizzard) for finding the problem
 """
-from __future__ import annotations
-
-import math
 
 
 def prime_sieve(num: int) -> list[int]:
@@ -33,32 +30,34 @@ def prime_sieve(num: int) -> list[int]:
     []
     """
 
-    if num <= 0:
-        raise ValueError(f"{num}: Invalid input, please enter a positive integer.")
+    if num < 2:
+        return []
 
     sieve = [True] * (num + 1)
-    prime = []
-    start = 2
-    end = int(math.sqrt(num))
+    sieve[0] = sieve[1] = False
 
-    while start <= end:
-        # If start is a prime
-        if sieve[start] is True:
-            prime.append(start)
+    # Do even numbers separately
+    primes = [2]
+    for i in range(4, num + 1, 2):
+        sieve[i] = False
 
-            # Set multiples of start be False
-            for i in range(start * start, num + 1, start):
-                if sieve[i] is True:
-                    sieve[i] = False
+    p = 3
+    while p * p <= num:
+        # If p is a prime
+        if sieve[p] is True:
+            primes.append(p)
 
-        start += 1
+            # Set multiples of start be False
+            for i in range(p * p, num + 1, p):
+                sieve[i] = False
+        p += 2
 
-    for j in range(end + 1, num + 1):
-        if sieve[j] is True:
-            prime.append(j)
+    for i in range(p, num + 1, 2):
+        if sieve[i] is True:
+            primes.append(i)
 
-    return prime
+    return primes
 
 
 if __name__ == "__main__":
-    print(prime_sieve(int(input("Enter a positive integer: ").strip())))
+    print(prime_sieve(int(input("Get all primes less than or equal to: ").strip())))