Meta·Software Engineer·Technical Phone Screen·Intermediate

Intermediate

Jun 2026

Summary

Meta Production Engineer interview with a string parsing problem that looks deceptively simple until you actually try to implement it cleanly. Two pointers, edge cases everywhere.

Questions Asked (1)

Given a string and an abbreviation, write a function to determine whether the abbreviation is valid. An abbreviation replaces one or more non-adjacent substrings with their lengths, and numbers can't have leading zeros.

Algorithms & Data Structures

Author's notes

Went in thinking this was easy and got humbled by the edge cases pretty fast.

Create a free account to read the full note

AI HintsAI Generated

Suggested Approach

Use a two-pointer technique to traverse the abbreviation and the target string simultaneously, parsing numbers in the abbreviation as skip counts. Validate that numbers have no leading zeros and that the total skipped characters align exactly with the string length.

Pro tip: Clarify edge cases upfront (empty string, abbreviation with only numbers, leading zeros) and discuss time/space complexity—O(n) time and O(1) space—to demonstrate thoroughness and efficiency awareness.

1. Clarify requirements and edge cases

Confirm assumptions: abbreviation may contain letters and digits, numbers represent skips, no leading zeros, and the entire string must be consumed. Discuss edge cases like empty string, abbreviation starting with zero, or consecutive numbers.

2. Design two-pointer traversal

Use pointers i for the string and j for the abbreviation. Iterate while j < len(abbr): if abbr[j] is a letter, compare with string[i] and advance both; if digit, parse the full number and advance i by that number.

3. Handle number parsing and leading zeros

When encountering a digit, ensure it's not '0' (leading zero invalid). Parse consecutive digits into an integer, then advance i by that integer. If i exceeds string length, return false.

4. Validate final alignment

After processing the abbreviation, check that both pointers have reached the end (i == len(string) and j == len(abbr)). If not, the abbreviation is invalid.

5. Analyze complexity and test

State time complexity O(n) and space O(1). Walk through examples (e.g., 'internationalization' vs 'i12iz4n') and edge cases to verify correctness.

Key Points to Mention

Two-pointer technique for simultaneous traversal
Parsing numbers as skip counts and rejecting leading zeros
Ensuring the entire string is consumed exactly
Handling edge cases: empty string, abbreviation with only digits, invalid characters
Time complexity O(n) and space complexity O(1)
Clear variable naming and modular code structure

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.