Remove Nth Node from List End

Author: anantkaushik

Python/Interviewbit/Linked_Lists/remove-nth-node-from-list-end.py

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+"""
+Problem Link: https://www.interviewbit.com/problems/remove-nth-node-from-list-end/
+
+Given a linked list, remove the nth node from the end of list and return its head.
+
+For example,
+Given linked list: 1->2->3->4->5, and n = 2.
+After removing the second node from the end, the linked list becomes 1->2->3->5.
+
+Note:
+If n is greater than the size of the list, remove the first node of the list.
+Try doing it using constant additional space.
+"""
+# Definition for singly-linked list.
+# class ListNode:
+#    def __init__(self, x):
+#        self.val = x
+#        self.next = None
+
+class Solution:
+    # @param A : head node of linked list
+    # @param B : integer
+    # @return the head node in the linked list
+    def removeNthFromEnd(self, A, B):
+        fast = A
+        for _ in range(B):
+            if fast:
+                fast = fast.next
+            else: 
+                break
+        if not fast or not fast.next:
+            return A.next
+        
+        slow = A
+        while fast and fast.next:
+            fast = fast.next
+            slow = slow.next
+        slow.next = slow.next.next
+        return A