Count minimum cost in string
Last updated: May 19, 2026
Quick Overview
Given a string consisting of lowercase letters, you need to calculate the minimum cost to convert the string into a palindrome. The cost is defined as the sum of the absolute differences between the ASCII values of characters that need to be changed to achieve the palindrome. Your function should take the input string and return the minimum cost as an integer.
Goldman Sachs
May 19, 202684
6
3,212 solved
Given a string consisting of lowercase letters, you need to calculate the minimum cost to convert the string into a palindrome. The cost is defined as the sum of the absolute differences between the ASCII values of characters that need to be changed to achieve the palindrome. Your function should take the input string and return the minimum cost as an integer.
Coding interviews at Goldman Sachs 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
- Can you solve this in a single pass?
- How would you test this solution thoroughly?
- Can you optimize the space complexity of your solution?
- How would you parallelize this solution?
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Practice DSA ProblemsSample Answer
Problem Analysis
To solve the problem of converting the given string into a palindrome at the minimum cost, we can utilize the two-pointer technique. This approach is relevant because a palindrome reads the same f...
Approach
- Initialize Pointers: Set two pointers, one at the beginning (left) and one at the end (right) of the string.
- Cost Calculation: While the left pointer is less than the right pointer, comp...
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