Create counting-elements.py

Author: kamyu104

Python/counting-elements.py

@@ -0,0 +1,31 @@
+# Time:  O(n)
+# Space: O(n)
+
+class Solution(object):
+    def countElements(self, arr):
+        """
+        :type arr: List[int]
+        :rtype: int
+        """
+        lookup = set(arr)
+        return sum(1 for x in arr if x+1 in lookup)
+
+
+# Time:  O(nlogn)
+# Space: O(1)
+class Solution(object):
+    def countElements(self, arr):
+        """
+        :type arr: List[int]
+        :rtype: int
+        """
+        arr.sort()
+        result, l = 0, 1
+        for i in xrange(len(arr)-1):
+            if arr[i] == arr[i+1]:
+                l += 1
+                continue
+            if arr[i]+1 == arr[i+1]:
+                result += l
+            l = 1
+        return result