beingsde
Sign In
Back to all DSA patterns
Linked List•Pattern: Simulation•Medium

Add two numbers represented as reversed linked lists

Problem Intuition & Objective

Sum two numbers stored digit-by-digit in reverse order in linked lists.

Time ComplexityO(max(m,n))
Optimal
Space ComplexityO(max(m,n))
Memory Bounds
Optimal Algorithmic Approach

Simultaneous traversal with carry propagation.

Core Invariants & Edge Cases

  • Traverse both lists simultaneously, summing digits + carry
  • Create a new node for each digit sum % 10; carry = sum / 10
  • Don't forget a final carry node after both lists are exhausted
Previous ProblemRemove the Nth node from the end of a linked listNext Problem Deep copy a linked list with random pointers

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.