Product of Array Except Self

Product of Array Except Self | AlgoChronicle

Step 1

Know these before you start

Tick what you already know

Concept video

Step 2

Try it on paper

5–10 minutes, no code yet

ProblemProblem statementGiven an integer array nums, return an array answer such that answer[i] equals the product of all the elements of nums except nums[i]. You must not use division, and the solution must run in O(n) time.Read

Problem Statement

Given an integer array nums, return an array answer such that answer[i] equals the product of all the elements of nums except nums[i]. You must not use division, and the solution must run in O(n) time.

Imported 2026-10-09 from NeetCode auto-sync. Note: the synced submissions were the O(n²) brute force — kept below, with the O(n) optimized version added.

Input / Output

Input:  nums = [1,2,3,4]
Output: [24,12,8,6]

Step 6

Get it accepted

All test cases pass

Step 7

Review it so it sticks

Re-solve from memory after

Solve it yourself before you look

Reading the solution first feels like progress, but it makes the next similar problem — and the interview version — much harder, because you skipped the part where you figure it out. Give it an honest 20–30 minutes. Stuck? Re-read the pattern, watch the concept video, or try the brute force first.

Hidden: approach · solution code · optimal solution

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