Count kth largest element in array
Last updated: October 28, 2025
Quick Overview
Given an unsorted array of integers, write a function to find the kth largest element in the array. The function should take the array and an integer k as input and return the kth largest element. Note that k is guaranteed to be between 1 and the length of the array.
Compass
October 28, 20256
5
4,041 solved
Given an unsorted array of integers, write a function to find the kth largest element in the array. The function should take the array and an integer k as input and return the kth largest element. Note that k is guaranteed to be between 1 and the length of the array.
Compass uses this problem in the Take-home Project to evaluate your algorithmic thinking. They expect you to discuss multiple approaches, analyze trade-offs between them, and implement the optimal solution with clean, readable code.
What the Interviewer Expects
- Recognize the underlying problem pattern (sliding window, two pointers, BFS/DFS, etc.)
- Discuss multiple approaches and trade-offs before coding
- Implement an optimal solution with clean, production-quality code
- Handle all edge cases including boundary conditions and invalid input
- Optimize both time and space complexity with clear justification
- Test your solution systematically with well-chosen examples
Key Topics to Cover
How to Approach This
- Clarify input constraints and edge cases before writing code.
- Walk through your approach verbally and confirm with the interviewer before coding.
- Start with a brute force solution, then optimize. Mention time and space complexity.
- Test your solution with examples, including edge cases like empty input or duplicates.
- Consider common patterns: sliding window, two pointers, hash map, BFS/DFS, dynamic programming.
Possible Follow-up Questions
- Can you solve this iteratively instead of recursively (or vice versa)?
- How would you parallelize this solution?
- How would your solution change if the input was sorted?
- What is the worst-case input for your solution?
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Practice DSA ProblemsSample Answer
Problem Analysis
To solve the problem of finding the kth largest element in an unsorted array, we can recognize that this is a typical selection problem. Given that k is guaranteed to be between 1 and the length of th...
Approach
Here's the step-by-step algorithm using the Quickselect method:
- Choose a Pivot: Randomly select a pivot element from the array.
- Partitioning: Rearrange the array elements such that those...
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