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