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Count subarrays equal to target

Akuna CapitalData Scientist · Technical Screen
MediumData ScientistTechnical ScreenCoding & Algorithms

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This interview question evaluates algorithm design, data structures, correctness, complexity, edge cases, and implementation details in a realistic interview setting. A strong answer for Count subarrays equal to target states assumptions, handles edge cases, explains trade-offs, and shows how to validate the result clearly.

Given an integer array nums and an integer k, count the number of contiguous subarrays whose sum equals k. Solve it in O(n) time and O(n) space by maintaining a running prefix sum and a hash map of prefix-sum frequencies. Explain why this works with negative numbers, analyze complexity, and provide code or pseudocode.