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"
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.

 思路：双指针，用j来循环t，如果找到了s.charAt(i), 那么i++，如果i == s.length()，就证明我找完了。

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