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Odd Even Linked List

MediumLinked list
Solve on LeetCode

Medium · linked-list walk solution for Odd Even Linked List. Python, Go, and a step-by-step animation.

01

Problem

Read the prompt, flip through the examples, then steal the idea.

LeetCode 328. Odd Even Linked List. The copyrighted prompt is on LeetCode. This page is a working linked-list walk solution for this problem: editable input, Python, Go, and a step-by-step animation.

Constraints

  • —Player inputs are capped so the animation stays readable.
  • —Match LeetCode's own constraints when you submit there.

Examples

Input

head =
[1, 2, 3, 4]

Output

[4,3,2,1]

Each node is peeled off cur and pushed onto prev.

02

Solution

Python and Go. The walkthrough below runs this same code.

Approach 1Optimal▶ Animated

Odd Even Linked List — linked-list walk

Three pointers: prev, cur, next. Flip one edge per step. Built for LeetCode 328. Odd Even Linked List.

You only ever need the next node saved before you rewire cur.next = prev. Walk until cur is nil; prev is the new head.

Algorithm

  1. prev = null, cur = head.
  2. Save next, flip the edge, slide prev and cur forward.
  3. Return prev.
Time
O(n)
Space
O(1)
Solution.py
class Solution:    def oddEvenLinkedList(self, head: list[int]) -> list[int]:        prev: list[int] = []        cur = head        while cur:            nxt = cur[1:]            prev = [cur[0], *prev]            cur = nxt        return prev
Watch this run

03

Interactive walkthrough

Playing “Odd Even Linked List — linked-list walk”. Edit the input, hit Run, then scrub.

Approach: Odd Even Linked List — linked-list walk

Loading animation…