1032. Stream of Characters.java

class StreamChecker {
    
    class Node{
        /* suffix trie */
        Node[] childs = new Node[26];
        boolean isEnd = false;
    }
    
    private final Node root;
    private final StringBuilder sb;

    public StreamChecker(String[] words)
    {
        root = new Node();
        sb = new StringBuilder();
        
        for(String s : words)
        {
            Node curr = root;
            for(int i = s.length()-1; i >= 0; i--)
            {
                char ch = s.charAt(i);
                if(curr.childs[ch-'a'] == null)
                {
                    curr.childs[ch-'a'] = new Node();
                }
                curr = curr.childs[ch-'a'];
            }
            
            curr.isEnd = true;
        }
    }

    public boolean query(char letter) {
        
        sb.append(letter);
        Node curr = root;
        for(int i = sb.length()-1; i >= 0; i--)
        {
            char ch = sb.charAt(i);
            curr = curr.childs[ch-'a'];
            if(curr == null)
                return false;
            if(curr.isEnd == true)
                return true;
        }
        return false;
    }
}

/**
 * Your StreamChecker object will be instantiated and called as such:
 * StreamChecker obj = new StreamChecker(words);
 * boolean param_1 = obj.query(letter);
 */