237. Delete Node in a Linked List

Problem

Write a function to delete a node (except the tail) in a singly linked list, given only access to that node.

Given linked list -- head = [4,5,1,9], which looks like following:

4->5->1->9

Example 1:

Input: head = [4,5,1,9], node = 5 Output: [4,1,9] Explanation: You are given the second node with value 5, the linked list should become 4 -> 1 -> 9 after calling your function.

Example 2:

Input: head = [4,5,1,9], node = 1 Output: [4,5,9] Explanation: You are given the third node with value 1, the linked list should become 4 -> 5 -> 9 after calling your function.

Note:

  • The linked list will have at least two elements.
  • All of the nodes' values will be unique.
  • The given node will not be the tail and it will always be a valid node of the linked list.
  • Do not return anything from your function.

Thought Process

  • The problem only provided the node, not head node, so we can't traverse the linked list to find the node to delete.
  • An easy way to solve is to replace the node's current value with the next node value

White Board

Below is the white board:

Code

class LN:
    def __init__(self, val):
        self.val = val
        self.next = None

class Sol:
    def deleteNode(self, node):

        if node is not None:
            delnode = node.next
            node.val = delnode.val

            #find the next node to replace/delete
            if delnode.next is not None:
                node.next = delnode.next
            else:
                node.next = None

        node = None

Complexity

  • Time complexity is O(1), space complexity is O(n) as well

Optimization

TODO How to improve?