Given two strings s and t, return true if s is a subsequence of t, or false otherwise.

A subsequence of a string is a new string that is formed from the original string by deleting some (can be none) of the characters without disturbing the relative positions of the remaining characters. (i.e., "ace" is a subsequence of "abcde" while "aec" is not).

  Example 1: Input: s = "abc", t = "ahbgdc" Output: true Example 2: Input: s = "axc", t = "ahbgdc" Output: false

  Constraints:

0 <= s.length <= 100
0 <= t.length <= 10⁴
s and t consist only of lowercase English letters.

  Follow up: Suppose there are lots of incoming s, say s₁, s₂, ..., sk where k >= 10⁹, and you want to check one by one to see if t has its subsequence. In this scenario, how would you change your code?