Leetcode Q392. Is Subsequence (Q322)

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?

Complexity:

Time: O(n)
Space: O(1)

Code:

/**
* @param {string} s
* @param {string} t
* @return {boolean}
*/
var isSubsequence = function(s, t) {
if (!s.length) return true;
let i = 0;
for (let c of t)
if (s[i] == c && ++i == s.length)
return true;
return false;
};

isSubsequence(“abc”, “ahbgdc”)

O/P:

true