237. Delete Node in a Linked List

https://leetcode.com/problems/delete-node-in-a-linked-list/

Level: Medium (should be Easy)

Initial Solution

Time: $\mathcal{O}(n)$

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

class Solution:
    def deleteNode(self, node):
        """
        :type node: ListNode
        :rtype: void Do not return anything, modify node in-place instead.
        """
        cur = node
        next = node.next
        while next is not None:
            cur.val = next.val
            if next.next is None:
                cur.next = None
                break
            cur = next
            next = cur.next

Optimized Solution

Time: $\mathcal{O}(1)$

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

class Solution:
    def deleteNode(self, node):
        """
        :type node: ListNode
        :rtype: void Do not return anything, modify node in-place instead.
        """
        node.val = node.next.val
        node.next = node.next.next