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).

  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?

Solution

/**
 * @param {string} s
 * @param {string} t
 * @return {boolean}
 */
var isSubsequence = function(s, t) {
    var j = 0;
    for (var i = 0; i < s.length; i++) {
        while (s[i] !== t[j] && j < t.length - 1) j++;
        if (s[i] != t[j]) return false;
        j++;
    }
    return true;
};

Explain:

nope.

Complexity:

• Time complexity : O(n).
• Space complexity : O(1).