Two Pointers on grid
Last updated: November 16, 2025
Quick Overview
Given a 2D grid of integers, use the two-pointer technique to find the maximum sum of a path from the top-left corner to the bottom-right corner, where you can only move right or down. The function should return the maximum sum as an integer.
ServiceNow
November 16, 2025496
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3,453 solved
Given a 2D grid of integers, use the two-pointer technique to find the maximum sum of a path from the top-left corner to the bottom-right corner, where you can only move right or down. The function should return the maximum sum as an integer.
This coding problem is frequently asked during Phone Screen at ServiceNow. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. ServiceNow 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
- How would you parallelize this solution?
- How would you test this solution thoroughly?
- How would your solution change if the input was sorted?
- Can you solve this iteratively instead of recursively (or vice versa)?
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Practice DSA ProblemsSample Answer
Problem Analysis
This problem can be approached using a dynamic programming technique rather than the traditional two-pointer technique since we need to calculate the maximum sum path in a grid. The reason for using d...
Approach
- Initialize a 2D list
dpof the same dimensions as the grid, where each cell will eventually hold the maximum sum to reach that cell. - Set
dp[0][0]togrid[0][0]since that's our starting po...
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