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Remove Nth Node From End of List

Medium
Fast & Slow Pointers

Given the head of a linked list, remove the nth node from the end of the list and return its head.

This problem uses a variation of the two-pointer technique where the gap between pointers helps us locate a specific position from the end. By maintaining a fixed gap of n nodes between two pointers and advancing both until the fast pointer reaches the end, the slow pointer will be perfectly positioned.

Example 1

Input: head = [1,2,3,4,5], n = 2
Output: [1,2,3,5]
Explanation: We remove the 2nd node from the end (value 4).

Example 2

Input: head = [1], n = 1
Output: []
Explanation: The only node is removed, resulting in an empty list.

Example 3

Input: head = [1,2], n = 1
Output: [1]
Explanation: We remove the last node (value 2).

Constraints

  • •The number of nodes in the list is sz
  • •1 <= sz <= 30
  • •0 <= Node.val <= 100
  • •1 <= n <= sz
Show Hints (4)
Hint 1: If you knew the length of the list, which node would you remove (from the beginning)?
Hint 2: Can you determine the position without first counting all nodes?
Hint 3: What if one pointer gets a head start of n nodes?
Hint 4: Consider using a dummy node before head to handle the case of removing the first node elegantly.
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