Dynamic Programming on string
Last updated: February 13, 2026
Quick Overview
Given a string, implement a function to determine the length of the longest palindromic substring using dynamic programming. The function should take a single input string and return an integer representing the length of the longest palindromic substring found within it.
HubSpot
February 13, 20265
14
3,951 solved
Given a string, implement a function to determine the length of the longest palindromic substring using dynamic programming. The function should take a single input string and return an integer representing the length of the longest palindromic substring found within it.
Coding interviews at HubSpot 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
- How would your solution change if the input was sorted?
- What is the worst-case input for your solution?
- Can you solve this iteratively instead of recursively (or vice versa)?
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Practice DSA ProblemsSample Answer
Problem Analysis
To solve the problem of finding the longest palindromic substring, we can utilize the dynamic programming approach. A palindrome reads the same forwards and backwards, and we can build our solution by...
Approach
- Initialize a 2D array
dpof sizen x n, wherenis the length of the input string. Set all entries toFalse. - Each single character is a palindrome, so set
dp[i][i] = Truefor allif...
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