beingsde
Sign In
Back to all DSA patterns
Linked List•Pattern: Slow/Fast Pointer + In-place Reversal•Medium

Reorder linked list: L0→L1→…→Ln becomes L0→Ln→L1→Ln-1→…

Problem Intuition & Objective

Reorder a linked list in-place by interleaving from front and back.

Time ComplexityO(n)
Optimal
Space ComplexityO(1)
Memory Bounds
Optimal Algorithmic Approach

Three-step: find mid → reverse second half → merge.

Core Invariants & Edge Cases

  • Find the middle using slow/fast pointers
  • Reverse the second half
  • Merge the two halves alternately
Previous ProblemDetect and find the start of a cycle in a linked listNext Problem Remove the Nth node from the end of a linked list

System Design & Architecture Roadmap

Coding interviews are only 50% of the bar. Master High-Level Design, distributed systems, and Object-Oriented LLD.

60+ HLD QuestionsSharding, caching, and real-time distributed systems.27 LLD BlueprintsObject-oriented design patterns with class diagrams.SDE Quick ReferenceLatency numbers and database selection matrix.