Delete Node in a Linked List
Medium · Linked Lists · Linked List
Problem
You are handed a reference to one node inside a singly linked list, but not the head of the list. Remove that node's value from the list.
The node is never the last one, and all values in the list are distinct. You cannot reach the node before it, so "deleting" means that afterwards:
- the given node's value no longer appears in the list,
- the list is one node shorter, and
- every other value keeps its original relative order.
In the tests, values is the whole list and target is the value of the node you receive; the grader builds the list, calls deleteNode with that node only, and reads the list back from its head.
Examples
Input: values = [3,8,1,6], target = 8 Output: [3,1,6]
The node holding 8 takes the value 1 from the next node and skips that node, so 8 disappears and the list reads 3, 1, 6.
Input: values = [10,20], target = 10 Output: [20]
The head node takes the value 20 and drops the old second node.
Input: values = [4,5,9,2], target = 9 Output: [4,5,2]
The node before the tail copies 2 and unlinks the tail.
Constraints
- 2 <= number of nodes <= 1000
- -1000 <= Node.val <= 1000
- All values are distinct
- The given node is in the list and is not the tail
Approaches
- Slide every later value left — time O(n), space O(1)
Follow-up
Why can the node not be the tail? There is no successor to copy, and without the previous node nothing can drop the tail. Some designs keep a dummy sentinel at the end of every list for exactly this reason: then every real node has a successor.
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