beingsde
Sign In
Back to all DSA patterns
Array•Pattern: Prefix / Suffix Product•Medium

Product of array except self

Problem Intuition & Objective

Return an array where each element is the product of all other elements — no division allowed.

Time ComplexityO(n)
Optimal
Space ComplexityO(1) extra (output array excluded)
Memory Bounds
Optimal Algorithmic Approach

Two-pass: left-to-right pass fills prefix products, right-to-left pass multiplies in suffix products using a single running variable.

Core Invariants & Edge Cases

  • Build prefix products left-to-right into the result array
  • Then sweep right-to-left maintaining a running suffix product
  • Combine: result[i] = prefix[i] × suffix[i]
Previous ProblemFind the majority element in an array (appears > n/2 times)Next Problem Maximum subarray sum (Kadane's Algorithm)

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.