Greedy on grid
Last updated: March 1, 2026
Quick Overview
Given a grid of integers, implement a greedy algorithm to find the maximum sum of values collected by moving from the top-left corner to the bottom-right corner, only being allowed to move right or down. The input will be a 2D array representing the grid, and the output should be a single integer representing the maximum sum.
Shopify
March 1, 2026372
10
4,601 solved
Given a grid of integers, implement a greedy algorithm to find the maximum sum of values collected by moving from the top-left corner to the bottom-right corner, only being allowed to move right or down. The input will be a 2D array representing the grid, and the output should be a single integer representing the maximum sum.
Coding interviews at Shopify 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
- How would you parallelize this solution?
- Can you solve this in a single pass?
- Can you solve this iteratively instead of recursively (or vice versa)?
- What happens if the input contains duplicates?
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Practice DSA ProblemsSample Answer
Problem Analysis
The problem requires us to find the maximum sum of values collected while traversing a grid from the top-left corner to the bottom-right corner, with restrictions on movement (only right or down). Thi...
Approach
- Initialization: Create a 2D list
dpof the same dimensions as the grid to store the maximum sum at each cell. - Base Case: Set
dp[0][0]togrid[0][0]since that's the starting point....
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