Count kth largest element in matrix
Last updated: November 16, 2025
Quick Overview
Given a 2D matrix of integers, write a function to find the kth largest element in the matrix. The function should take the matrix and an integer k as inputs and return the kth largest element. The matrix is guaranteed to have at least k elements.
Scale AI
November 16, 202525
4
3,690 solved
Given a 2D matrix of integers, write a function to find the kth largest element in the matrix. The function should take the matrix and an integer k as inputs and return the kth largest element. The matrix is guaranteed to have at least k elements.
Coding interviews at Scale AI focus on problem-solving approach as much as the final solution. The interviewer wants to see you break down the problem, consider edge cases, and optimize iteratively. Communication throughout the process is key.
What the Interviewer Expects
- Identify the correct data structure and algorithm for the problem
- Write clean, bug-free code with proper variable naming
- Analyze time and space complexity correctly
- Handle basic edge cases (empty input, single element)
- Communicate your thought process while coding
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)?
- What is the worst-case input for your solution?
- What if the input doesn't fit in memory?
- Can you optimize the space complexity of your solution?
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Problem Analysis
To solve the problem of finding the kth largest element in a 2D matrix, we can leverage the properties of heaps, specifically a min-heap. Since we need to maintain the largest k elements in the matrix...
Approach
- Initialize a min-heap to keep track of the largest k elements encountered so far.
- Iterate through each element in the 2D matrix.
- For each element, if the size of the min-heap is less than k, ...
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