LeetCode 18 - Delete Node in a Linked List

Delete Node in a Linked List

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:

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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:

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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.

Solution

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# Definition for singly-linked list.
# class ListNode(object):
# def __init__(self, x):
# self.val = x
# self.next = None
class Solution(object):
def deleteNode(self, node):
next = node.next
if next:
node.val = next.val
node.next = next.next

Pretty self explanatory. Runs and has space in O(1). You can’t delete from the tail, in which case you would raise an exception if there is no next pointer, but that was an assumption here that it would be valid.