started euler project problems. Problem 1 solved

Author: shiv

multiples_of_3_5.py

@@ -0,0 +1,43 @@
+# multiples of 3 and 5
+
+'''
+EULER:
+
+If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23.
+
+Find the sum of all the multiples of 3 or 5 below 1000.
+
+Performance:
+233168
+finished in: 0.0001709461212158203
+
+Performance with extra condition (avoiding re computations):
+233168
+finished in: 9.894371032714844e-05
+
+'''
+
+import time
+
+n = 1000
+
+def get_multiples(n):
+    multiples = set()
+    for i in range(1,n):
+        val = 3*i
+        if val<n: multiples.add(val)
+        else:break
+    for i in range(1,n):
+        # a condition to speed it up
+        if i%3 == 0:
+            # because all the previous multiples of 3 are covered
+            continue
+        val = 5*i
+        if val<n: multiples.add(val)
+        else:break
+    return sum(multiples)
+
+
+start =time.time()
+print(get_multiples(n))
+print('finished in:', time.time()-start)