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 <= 10^4

• s and t consist only of lowercase English letters.

  Follow up: Suppose there are lots of incoming s, say s1, s2, ..., sk where k >= 10^9, 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

class Solution {
    public boolean isSubsequence(String s, String t) {
        int i = 0;
        int j = 0;
        int n = t.length();
        int m = s.length();
        if (m == 0) {
            return true;
        }
        while (j < n) {
            if (s.charAt(i) == t.charAt(j)) {
                i++;
                if (i == m) {
                    return true;
                }
            }
            j++;
        }
        return false;
    }
}

Explain:

nope.

Complexity:

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