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Determine most popular concert city

Last updated: Mar 29, 2026

Quick Overview

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

  • medium
  • Microsoft
  • Coding & Algorithms
  • Software Engineer

Determine most popular concert city

Company: Microsoft

Role: Software Engineer

Category: Coding & Algorithms

Difficulty: medium

Interview Round: Technical Screen

##### Question Given a set of concert venue vote records, determine which city is the most popular. How would you normalize city names that have multiple spellings (e.g., 'NYC', 'New York')? If votes carry different weights, how would you incorporate them? Describe how you would scale the solution for large datasets.

Quick Answer: This interview question evaluates algorithm design, data structures, correctness, complexity, edge cases, and implementation details in a realistic interview setting. A strong answer for Determine most popular concert city states assumptions, handles edge cases, explains trade-offs, and shows how to validate the result clearly.

Solution

# Solution Alignment The prompt asks for an implementation-level answer. The safest way to present it is to define the state, maintain clear invariants, then walk through complexity and tests. ## Problem Restatement ##### Question Given a set of concert venue vote records, determine which city is the most popular. How would you normalize city names that have multiple spellings (e.g., 'NYC', 'New York')? If votes carry different weights, how would you incorporate them? Describe how you would scale the solution for large datasets. ## Recommended Approach Start with a brute-force baseline to confirm correctness, then identify the repeated work or ordering property that enables a better data structure such as a hash map, heap, stack, queue, two pointers, prefix sums, BFS/DFS, or dynamic programming. Write the implementation around a small invariant and test that invariant directly. ## Correctness The implementation should maintain an invariant after each loop or operation that directly matches the problem statement. At termination, that invariant implies the returned value has considered every valid candidate exactly once, or has preserved the required data-structure state after every API call. ## Complexity State the baseline complexity and the optimized complexity. For most interview constraints, justify why the optimized approach meets the expected input size. ## Edge Cases and Tests Empty and singleton inputs, duplicates, ties, invalid inputs, boundary values, and tests that exercise the main invariant.

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|Home/Coding & Algorithms/Microsoft

Determine most popular concert city

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Microsoft
Aug 4, 2025, 10:55 AM
mediumSoftware EngineerTechnical ScreenCoding & Algorithms
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Determine most popular concert city

Given a set of concert venue vote records, determine which city is the most popular. How would you normalize city names that have multiple spellings (e.g., 'NYC', 'New York')? If votes carry different weights, how would you incorporate them? Describe how you would scale the solution for large datasets.

Constraints & Assumptions

  • Preserve the scope, facts, inputs, and requested outputs from the prompt above.
  • If the prompt leaves a detail unspecified, state a reasonable assumption before relying on it.
  • Keep the answer interview-ready: concise enough to present, but concrete enough to implement or evaluate.

Clarifying Questions to Ask

  • Clarify input sizes, value ranges, mutability, return format, and tie-breaking.
  • State the target time and space complexity before coding.
  • Call out edge cases such as empty inputs, duplicates, invalid values, overflow, and boundary sizes.

What a Strong Answer Covers

  • A clear algorithm with the right data structures and enough pseudocode or code-level detail to implement it.
  • A correctness argument that explains why the algorithm covers all required cases.
  • Time and space complexity, plus at least one alternative approach when relevant.
  • Focused tests for normal cases, edge cases, and failure modes.

Follow-up Questions

  • How would the approach change if the input were streaming or too large for memory?
  • What invariants would you assert in production code?
  • Which tests would catch off-by-one, duplicate, or tie-breaking bugs?

Submit Your Answer to Earn 20XP

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