Remove_nth_node_from_end_of_list

Author: shichao-an

remove_nth_node_from_end_of_list/solution.py

@@ -0,0 +1,28 @@
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, x):
+#         self.val = x
+#         self.next = None
+
+class Solution:
+    # @return a ListNode
+    def removeNthFromEnd(self, head, n):
+        if head is None:
+            return None
+        elif n == 0:
+            return head
+        else:
+            q = p = pp = head  # `pp` is the node preceding `p`
+            while q is not None:
+                if n <= 0:
+                    pp = p
+                    p = p.next
+                q = q.next
+                n -= 1
+            # Remove the head node
+            if pp is p:
+                head = pp.next
+            else:
+                pp.next = p.next
+                # Free p
+            return head