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This is a medium difficulty Coding & Algorithms question, commonly asked during Technical Screen rounds at Cognitiv.

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This question is commonly asked for Machine Learning Engineer candidates at Cognitiv during technical interviews.

Maintain a Streaming Median | Cognitiv Interview Question

Maintain a Streaming Median

Last updated: Mar 29, 2026

Quick Overview

This question evaluates understanding of streaming algorithms and dynamic data structures for maintaining order statistics, along with analysis of time complexity and memory trade-offs.

Cognitiv

Feb 9, 2026, 12:00 AM

Machine Learning Engineer

Technical Screen

Coding & Algorithms

You are designing a component that receives integers one at a time and must return the current median after each update.

Example:

After processing [2, 3, 1] , the median is 2 .
After processing one more value to form [2, 3, 1, 4] , the median is (2 + 3) / 2 = 2.5 .

Implement a data structure with two operations:

add(x) : insert an integer
getMedian() : return the median of all inserted values so far

Discuss the time complexity of your approach.

Follow-up: if the full input array is available up front and you want to avoid extra auxiliary space, how would you compute the median while minimizing additional memory usage?

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