Leetcode 392. Is Subsequence

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).

Algorithm

Use two pointers to follow the two strings.

Code

class Solution:
    def isSubsequence(self, s: str, t: str) -> bool:
        sIndex, tIndex, sLen, tLen = 0, 0, len(s), len(t)
        while sIndex < sLen and tIndex < tLen:
            if s[sIndex] == t[tIndex]:
                sIndex += 1
                tIndex += 1
            else:
                tIndex += 1
        
        return sIndex >= sLen