0392-Is-Subsequence.py

'''
 Given a string s and a string t, check if s is subsequence of t.

You may assume that there is only lower case English letters in both s and t. t is potentially a very long (length ~= 500,000) string, and s is a short string (<=100).

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

Example 1:
s = "abc", t = "ahbgdc"

Return true.

Example 2:
s = "axc", t = "ahbgdc"

Return false.

Follow up:
If there are lots of incoming S, say S1, S2, ... , Sk where k >= 1B, and you want to check one by one to see if T has its subsequence. In this scenario, how would you change your code?
'''
class Solution:
    def isSubsequence(self, s: str, t: str) -> bool:
        s_index = t_index = 0
        
        while s_index < len(s) and t_index < len(t):
            if s[s_index] == t[t_index]:
                s_index += 1
            t_index += 1
        
        return s_index == len(s)