Create check-if-n-and-its-double-exist.py

Author: kamyu104

Python/check-if-n-and-its-double-exist.py

@@ -0,0 +1,16 @@
+# Time:  O(n)
+# Space: O(n)
+
+class Solution(object):
+    def checkIfExist(self, arr):
+        """
+        :type arr: List[int]
+        :rtype: bool
+        """
+        lookup = set()
+        for x in arr:
+            if 2*x in lookup or \
+               (x%2 == 0 and x//2 in lookup):
+                return True
+            lookup.add(x)
+        return False