Merge pull request #1676 from sprtkd/master

Added Sieve of Erathosthenes

IMPLEMENTATIONS.md

@@ -39,6 +39,7 @@
 * [Math](math)
   * [russian peasant](math/russian_peasant)
   * [towers of hanoi](math/towers_of_hanoi)
+  * [Sieve of Eratosthenes](math/sieve%20of%20eratosthenes)
   * [armstrong number](math/armstrong_number)
   * [euclid's gcd](math/euclids_gcd)
   * [prime seive](math/prime_seive)

math/sieve of eratosthenes/python/sieveOfEratosthenes.py

@@ -0,0 +1,28 @@
+def SieveOfEratosthenes(n):
+    '''
+    This function returns a list
+    which can be used for lookup of a number
+    to check whether it is prime or not
+
+    Input: max number to be looked up
+    
+    '''
+    prime = [True for i in range(n+1)] 
+    p = 2
+    while (p * p <= n): 
+        if (prime[p] == True):
+            for i in range(p * 2, n+1, p): 
+                prime[i] = False
+        p += 1
+
+    prime[0]=False
+    prime[1]=False
+    return prime
+
+
+if __name__ == "__main__" :
+    '''example use'''
+    max_val = 10
+    lookup_list = SieveOfEratosthenes(max_val)
+    for num in range(max_val+1):
+        print(num,': ', lookup_list[num])