Validate grid balanced
Last updated: February 9, 2026
Quick Overview
Given a 2D grid of integers, write a function to validate if the grid is balanced, meaning that the sum of each row is equal to the sum of each column. The function should return a boolean value: true if the grid is balanced, and false otherwise. The input will be a matrix of size m x n, where m and n are positive integers.
Dropbox
February 9, 202621
14
3,536 solved
Given a 2D grid of integers, write a function to validate if the grid is balanced, meaning that the sum of each row is equal to the sum of each column. The function should return a boolean value: true if the grid is balanced, and false otherwise. The input will be a matrix of size m x n, where m and n are positive integers.
Dropbox uses this problem in the Technical Screen 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
- Quickly identify the optimal approach and its theoretical basis
- Handle complex algorithm design with multiple interacting components
- Write concise, elegant code under time pressure
- Prove correctness of your approach and discuss alternative solutions
- Optimize beyond the obvious: discuss constant factor improvements
- Address follow-up variations and explain how the solution generalizes
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
- How would you test this solution thoroughly?
- How would you parallelize this solution?
- What is the worst-case input for your solution?
- Can you solve this in a single pass?
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Practice DSA ProblemsSample Answer
Problem Analysis
In this problem, we need to check if the sum of each row in a 2D grid is equal to the sum of each column. This situation can be effectively solved using a single pass approach leveraging the propertie...
Approach
- Initialize two lists,
row_sumsandcol_sums, of sizemandn, respectively, wheremis the number of rows andnis the number of columns in the grid. These will store the cumulative sum...
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