Added Sieve of Eratosthenes algorithm for finding primes

Author: RianGallagher

other/FindingPrimes.py

@@ -0,0 +1,21 @@
+'''
+-The sieve of Eratosthenes is an algorithm used to find prime numbers, less than or equal to a given value.
+-Illustration: https://upload.wikimedia.org/wikipedia/commons/b/b9/Sieve_of_Eratosthenes_animation.gif
+'''
+from math import sqrt
+def SOE(n):
+    check = round(sqrt(n)) #Need not check for multiples past the square root of n
+    
+    sieve = [False if i <2 else True for i in range(n+1)] #Set every index to False except for index 0 and 1
+    
+    for i in range(2, check):
+        if(sieve[i] == True):                  #If i is a prime  
+            for j in range(i+i, n+1, i):       #Step through the list in increments of i(the multiples of the prime)   
+                sieve[j] = False               #Sets every multiple of i to False 
+    
+    for i in range(n+1):
+        if(sieve[i] == True):
+            print(i, end=" ")
+
+n = int(input("Enter a positive number\n"))
+SOE(n)