392. Is Subsequence


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"

Example 2:

Input: s = "axc", t = "ahbgdc"


  • 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?


Runtime: 0 ms, faster than 100.00%

Memory Usage: 1.9 MB, less than 80.92%

func isSubsequence(s string, t string) bool {
    if len(s)==0 { return true }
    for i := 0; i < len(t); i++ {
        if t[i] == s[0] { s = s[1:] }
        if len(s)==0 { return true }
    return false

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