392. Is Subsequence

Problem Statement

link: LeetCode.cn LeetCode

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:

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

Input: s = "axc", t = "ahbgdc" Output: false

Solution Approach

The solution approach utilizes a two-pointer technique to traverse both strings simultaneously, checking for matching characters in order to determine if s is a subsequence of t.

Algorithm

1. Initialize two pointers p1 and p2 to track positions in s and t, respectively.
2. Iterate through both strings simultaneously, advancing pointers based on character matches.
3. If p1 reaches the end of s, return True; otherwise, return False.

Implement

    class Solution:
    def isSubsequence(self, s, t):
      p1, p2 = 0, 0
      while p1 < len(s) and p2 < len(t):
        if s[p1] == t[p2]:
          p1 += 1
        p2 += 1
      if p1 < len(s):
        return False
      return True
    
       

    
    

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