LEETCODEEasy

Is Subsequence

풀이일 2025 · 03 · 27기록 0 ms · 55.7 MB원문 leetcode ↗

Two PointersStringDynamic Programming

문제

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, ..., s_k 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?

풀이 TypeScript

function isSubsequence(s: string, t: string): boolean {

  const sLength = s.length
  let idx = 0;
  let str = t

  while(idx !== sLength) {
    const char = s[idx]
    const index = str.indexOf(char)
    if (index === -1) return false
    idx++
    str = str.slice(index + 1)
  }
  return true
}

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