Check if one string is a subsequence of another
Company: Atlassian
Role: Software Engineer
Category: Coding & Algorithms
Difficulty: medium
Interview Round: Technical Screen
Given two strings `s` and `t`, determine whether `s` is a **subsequence** of `t`.
A subsequence keeps relative order but does not require contiguous characters.
#### Input
- `s`: a string (may be empty)
- `t`: a string (may be empty)
#### Output
- Return `true` if `s` is a subsequence of `t`, otherwise return `false`.
#### Examples
- `s = "abc"`, `t = "aabzc"` → `true` (pick `a` at index 1, `b` at index 2, `c` at index 4)
- `s = "axc"`, `t = "ahbgdc"` → `false`
#### Constraints
- `0 ≤ |s|, |t| ≤ 10^5` (assume ASCII letters)
Follow-up (optional): If you need to answer this query for **dozens** of different `s` strings against the same `t`, what preprocessing (if any) would you do?
Quick Answer: This question evaluates understanding of string algorithms and subsequence detection, focusing on sequence traversal, edge-case handling, and time/space complexity reasoning.
Return whether s is a subsequence of t.
Constraints
- Inputs are Python literals matching the function signature.
- Return a deterministic exact-match value.
Examples
Input: ('abc','aabzc')
Expected Output: True
Explanation: abc appears in order.
Input: ('axc','ahbgdc')
Expected Output: False
Explanation: x cannot be matched.
Input: ('', 'anything')
Expected Output: True
Explanation: The empty string is a subsequence.
Input: ('abc','')
Expected Output: False
Explanation: A non-empty string is not a subsequence of empty t.
Hints
- Clarify edge cases before coding.
- Keep outputs deterministic when several valid answers exist.