Find kth largest element in matrix
Last updated: October 23, 2025
Quick Overview
Given a 2D matrix of integers where each row is sorted in ascending order, write a function to find the kth largest element in the matrix. The function should take the matrix and an integer k as input and return the kth largest element as output. The solution should be efficient, ideally using a min-heap or binary search approach.
Datadog
October 23, 2025258
6
2,323 solved
Given a 2D matrix of integers where each row is sorted in ascending order, write a function to find the kth largest element in the matrix. The function should take the matrix and an integer k as input and return the kth largest element as output. The solution should be efficient, ideally using a min-heap or binary search approach.
Coding interviews at Datadog 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
- 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
- What is the worst-case input for your solution?
- How would you modify your solution to handle streaming input?
- What if the input doesn't fit in memory?
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Problem Analysis
To solve the problem of finding the kth largest element in a 2D matrix where each row is sorted in ascending order, we can utilize a min-heap approach. The reason this pattern applies is that a mi...
Approach
- Initialize a min-heap: Start with an empty min-heap.
- Iterate through the matrix: Loop through each row and each element in the row.
- Add elements to the heap: For each element, a...
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