Count minimum cost in string
Last updated: July 13, 2025
Quick Overview
Given a string consisting of lowercase letters, 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 structure. Your function should take the string as input and return an integer representing the minimum cost.
Anduril
July 13, 2025130
13
542 solved
Given a string consisting of lowercase letters, 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 structure. Your function should take the string as input and return an integer representing the minimum cost.
Anduril uses this problem in the Phone 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
- 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
- What happens if the input contains duplicates?
- How would you modify your solution to handle streaming input?
- What is the worst-case input for your solution?
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Problem Analysis
To solve the problem of converting the given string into a palindrome at minimum cost, we can utilize a two-pointer technique. The idea is to compare characters from the start and end of the string, m...
Approach
- Initialize two pointers:
leftat the beginning of the string andrightat the end. - Initialize a variable
costto accumulate the total conversion cost. - While
leftis less thanright:...
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