Create Odd Even Linked List.py

Author: sugia

Odd Even Linked List.py

@@ -0,0 +1,54 @@
+'''
+Given a singly linked list, group all odd nodes together followed by the even nodes. Please note here we are talking about the node number and not the value in the nodes.
+
+You should try to do it in place. The program should run in O(1) space complexity and O(nodes) time complexity.
+
+Example 1:
+
+Input: 1->2->3->4->5->NULL
+Output: 1->3->5->2->4->NULL
+Example 2:
+
+Input: 2->1->3->5->6->4->7->NULL
+Output: 2->3->6->7->1->5->4->NULL
+Note:
+
+The relative order inside both the even and odd groups should remain as it was in the input.
+The first node is considered odd, the second node even and so on ...
+'''
+
+# Definition for singly-linked list.
+# class ListNode(object):
+#     def __init__(self, x):
+#         self.val = x
+#         self.next = None
+
+class Solution(object):
+    def oddEvenList(self, head):
+        """
+        :type head: ListNode
+        :rtype: ListNode
+        """
+        odd_dummy = ListNode(0)
+        odd_cur = odd_dummy
+        even_dummy = ListNode(0)
+        even_cur = even_dummy
+        
+        cur = head
+        count = 0
+        while cur:
+            count += 1
+            if count & 1:
+                odd_cur.next = cur
+                odd_cur = odd_cur.next
+            else:
+                even_cur.next = cur
+                even_cur = even_cur.next
+            cur = cur.next
+            
+        odd_cur.next = even_dummy.next
+        even_cur.next = None
+        
+        return odd_dummy.next
+        
+