Count kth largest element in array
Last updated: October 8, 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 two inputs: the array and an integer k, and it should return the kth largest element. Note that k is guaranteed to be between 1 and the length of the array.
Citadel
October 8, 2025213
7
610 solved
Given an unsorted array of integers, write a function to find the kth largest element in the array. The function should take two inputs: the array and an integer k, and it should return the kth largest element. Note that k is guaranteed to be between 1 and the length of the array.
This coding problem is frequently asked during Take-home Project at Citadel. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. Citadel expects candidates to write production-quality code, not just solve the puzzle.
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 in a single pass?
- How would you test this solution thoroughly?
- What happens if the input contains duplicates?
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Problem Analysis
To find the kth largest element in an unsorted array, we can leverage the properties of sorting. The problem can be approached using the quickselect algorithm, which is a variation of quicksort. This ...
Approach
- Select a Pivot: Choose a pivot element from the array.
- Partitioning: Rearrange the array such that elements greater than the pivot are on one side and elements less than the pivot are on...
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