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Linked List•Pattern: HashMap / Interleaving•Medium

Deep copy a linked list with random pointers

Problem Intuition & Objective

Clone a linked list where each node has a next and an arbitrary random pointer.

Time ComplexityO(n)
Optimal
Space ComplexityO(n) HashMap / O(1) in-place
Memory Bounds
Optimal Algorithmic Approach

HashMap (simpler) or in-place interleaving (O(1) space).

Core Invariants & Edge Cases

  • HashMap approach: map original → clone, then set next and random
  • In-place approach: interleave clones between originals, set randoms, then detach
  • In-place is O(1) space but tricky
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