isSubsequence

/*
Given a string s and a string t, check if s is subsequence of t.

A subsequence of a string is a new string which is formed from the original string by deleting some (can be none) of the characters without disturbing the relative positions of the remaining characters. (ie, "ace" is a subsequence of "abcde" while "aec" is not).

Follow up:
If there are lots of incoming S, say S1, S2, ... , Sk where k >= 1B, and you want to check one by one to see if T has its subsequence. In this scenario, how would you change your code?

Credits:
Special thanks to @pbrother for adding this problem and creating all test cases.

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
Both strings consists only of lowercase characters.
*/
class Solution {
    public boolean isSubsequence(String s, String t) {
        
        if(s.length()==0) return true;
        if(t.length()==0 || s.length()>t.length()) return false;
        
        return checkSub(s, 0, t,0);
    }
    
    boolean checkSub(String s, int sIndex, String t, int tIndex){
        
        if(sIndex >= s.length()) return true;
        if(tIndex >= t.length()) return false;
        
        boolean match=false, nomatch=false;
        if(s.charAt(sIndex)==t.charAt(tIndex)) {
            match=checkSub(s, sIndex+1, t, tIndex+1);
        }
        else{
            nomatch=checkSub(s, sIndex, t, tIndex+1);
        } 
        
        return match || nomatch;
    }
}