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Is Subsequence

Problem statement​

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?

My solution​

/**
 * @param {string} s
 * @param {string} t
 * @return {boolean}
 */
var isSubsequence = function(s, t) {
    if (!s.length) {
        return true;
    }
    
    let left = 0;
    let right = 0;
    
    while (right < t.length) {
        if (s[left] === t[right]) {
            left++;
            
            if (left === s.length) {
                return true;
            }
        }
        
        right++;
    }
    
    return false;
};