Is subsequence

class Solution:
    def isSubsequence(self, s: str, t: str) -> bool:
        @cache
        def dp(i, j):
            if i == len(s):
                return True
            if j == len(t):
                return False
            res = False
            if s[i] == t[j]:
                res = dp(i + 1, j + 1)
            else:
                res = res or dp(i, j + 1)
            return res

        return dp(0, 0)

Is Subsequence

Difficulty: Easy

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?