Problem

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:

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Input: s = "abc", t = "ahbgdc"
Output: true

Example 2:

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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

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s

, say

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s1, s2, ..., sk

where

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k >= 10^9

, and you want to check one by one to see if

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t

has its subsequence. In this scenario, how would you change your code?

Solve

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class Solution:
    def isSubsequence(self, s: str, t: str) -> bool:
        j = 0

        for i in range(len(s)):
            if s[i] not in t[j:]:
                return False
            else:
                j = j + t[j:].index(s[i]) +1

        return True

簡化一些

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class Solution:
    def isSubsequence(self, s: str, t: str) -> bool

        for i in range( len(s) ):
            if s[i] not in t:
                return False
            else:
                ii = t.index(s[i])
                t = t[ii + 1:]
        return True