392-IsSubsequence.py

# https://leetcode.com/problems/is-subsequence/

# 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). 

class Solution:
    def isSubsequence(self, s: str, t: str) -> bool:
        position = 0
        for char in s:
            if char in t[position:]:
                t = t[t[position:].index(char) + 1:]
            else:
                return False
        return True