LeetCode in TypeScript

392. Is Subsequence

Easy

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

function isSubsequence(s: string, t: string): boolean {
    let i = 0
    let j = 0
    const m = s.length
    const n = t.length
    if (m === 0) {
        return true
    }
    while (j < n) {
        if (s[i] === t[j]) {
            i++
            if (i === m) {
                return true
            }
        }
        j++
    }
    return false
}

export { isSubsequence }

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