Meta Follow-up for Custom Sort String (LC791)
- Posted
- 9 Feb 2025
Summary
I've shared my insights into Meta's interview style, specifically regarding the 'Custom Sort String' problem (LC791), its common variant, and a crucial optimization follow-up question.
How it went
From what I've observed in Meta interviews, they frequently pose the original LeetCode problem 791, 'Custom Sort String'. There's also a minor variant where the order parameter might be presented as a List rather than a string, though this typically doesn't alter the solution significantly. A key aspect of their assessment often comes with a follow-up question: optimizing the character frequency tracking from a HashMap<Character, Integer> to a List<Integer>, which is a good signal if you manage to solve it within time.
Questions asked (3)
- 01
Custom Sort String
Data Structures & Algorithms · Medium
Open the problemGiven two strings
orderands. All the characters oforderare unique and were sorted in some custom order previously. Permute the characters ofsso that they match the order thatorderwas sorted. More specifically, ifxoccurs beforeyinorder, thenxshould occur beforeyin the permuted string. Return any valid permutation ofs. - 02
Custom Sort String (List Order Variant)
Data Structures & Algorithms · Medium
The problem is identical to 'Custom Sort String', but the
orderparameter is provided as aList<Character>instead of astring. The core logic for sorting characters based on the custom order remains the same, requiring only minor adaptations for handling a list instead of a string. - 03
Optimize Custom Sort String Frequency Counting
Data Structures & Algorithms · Medium
If the solution for 'Custom Sort String' uses a
HashMap<Character, Integer>to store character frequencies, how would you optimize this to use aList<Integer>instead? This typically implies using a fixed-size array (e.g.,int[26]for lowercase English letters) to map character ASCII values to array indices for O(1) access.
How they prepared
I've detailed my approach and a solution for the original problem, its variant, and the follow-up optimization in my YouTube video. This resource aims to help others prepare effectively for this specific problem pattern often encountered in Meta interviews.