Check if one string is a subsequence of another

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?