Linked List pattern

Reorder List

Given the head of a singly linked list, reorder it in place by interleaving nodes from the front and back so the order becomes first, last, second, second-to-last, and so on. Only the node links may be changed, not the values. Watch it run step by step, then write your own pseudocode and get it checked by AI.

  • LeetCode 143
  • Medium
  • 2 approaches
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Linked ListLeetCode 143

Medium

From the first idea to the best one

  1. 01 Brute force · array of node references O(n)O(n) space
  2. 02 Optimized · middle + reverse + merge O(n)O(1) space
Each approach plays step by step, with its time and space.

What you will learn

  • How to read Reorder List and spot the linked list pattern in it
  • Brute force · array of node references: O(n) time, O(n) space
  • Optimized · middle + reverse + merge: O(n) time, O(1) space
  • The pseudocode for each approach, its line lit as the animation runs
  • Practice: write your own pseudocode and get it checked

More Linked List

See Reorder List run, step by step

Sign in and this page opens on the animation, with all 9 Linked List problems beside it.

Sign in to open itSee plans

DSA comes with the all labs plan and every ChaiCode batch.