392-Is-Subsequence.js

/**
 * https://leetcode.com/problems/is-subsequence/description/
 * Difficulty:Medium
 *
 * Given a string s and a string t, check if s is subsequence of t.
 * You may assume that there is only lower case English letters in both s and t. t is potentially a very long (length ~= 500,000) string, and s is a short string (<=100).
 * A subsequence of a string is a new string which is formed from the original string by deleting some (can be none) of the characters without disturbing the relative positions of the remaining characters. (ie, "ace" is a subsequence of "abcde" while "aec" is not).
 *
 * Example 1:
 * s = "abc", t = "ahbgdc"
 * Return true.
 *
 * Example 2:
 * s = "axc", t = "ahbgdc"
 * Return false.
 *
 * Follow up:
 * If there are lots of incoming S, say S1, S2, ... , Sk where k >= 1B, and you want to check one by one to see if T has its subsequence. In this scenario, how would you change your code?
 */

/**
 * @param {string} s
 * @param {string} t
 * @return {boolean}
 */
var isSubsequence = function (s, t) {
    var i = 0;
    var j = 0;
    var m = s.length;
    var n = t.length;
    while (j < n && i < m) {
        if (s[i] === t[j]) {
            i++;
        }
        j++;
    }

    return i === m;
};

console.log(isSubsequence('abc', 'asssbsssc'));
console.log(isSubsequence('abc', 'asssbsss'));
console.log(isSubsequence('', 'asssbsss'));