392. 判断子序列

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