import java.util.LinkedList;

public class TrieST<Value> {
	private static final int R = 256;        // extended ASCII

	private Node root;

	private static class Node {
		private Object val;
		private Node[] next = new Node[R];
	}

	/****************************************************
	 * Is the key in the symbol table?
	 ****************************************************/
	public boolean contains(String key) {
		return get(key) != null;
	}

	public Value get(String key) {
		Node x = get(root, key, 0);
		if (x == null) return null;
		return (Value) x.val;
	}

	private Node get(Node x, String key, int d) {
		if (x == null) return null;
		if (d == key.length()) return x;
		char c = key.charAt(d);
		return get(x.next[c], key, d+1);
	}

	/****************************************************
	 * Insert key-value pair into the symbol table.
	 ****************************************************/
	public void put(String key, Value val) {
		root = put(root, key, val, 0);
	}

	private Node put(Node x, String key, Value val, int d) {
		if (x == null) x = new Node();
		if (d == key.length()) {
			x.val = val;
			return x;
		}
		char c = key.charAt(d);
		x.next[c] = put(x.next[c], key, val, d+1);
		return x;
	}

	// find the key that is the longest prefix of s
	public String longestPrefixOf(String query) {
		int length = longestPrefixOf(root, query, 0, 0);
		return query.substring(0, length);
	}

	// find the key in the subtrie rooted at x that is the longest
	// prefix of the query string, starting at the dth character
	private int longestPrefixOf(Node x, String query, int d, int length) {
		if (x == null) return length;
		if (x.val != null) length = d;
		if (d == query.length()) return length;
		char c = query.charAt(d);
		return longestPrefixOf(x.next[c], query, d+1, length);
	}


	public Iterable<String> keys() {
		return keysWithPrefix("");
	}

	public Iterable<String> keysWithPrefix(String prefix) {
		LinkedList<String> queue = new LinkedList<String>();
		Node x = get(root, prefix, 0);
		collect(x, prefix, queue);
		return queue;
	}

	private void collect(Node x, String key, LinkedList<String> queue) {
		if (x == null) return;
		if (x.val != null) queue.add(key);
		for (int c = 0; c < R; c++)
			collect(x.next[c], key + (char) c, queue);
	}


	public Iterable<String> keysThatMatch(String pat) {
		LinkedList<String> q = new LinkedList<String>();
		collect(root, "", pat, q);
		return q;
	}

	public void collect(Node x, String prefix, String pat, LinkedList<String> q) {
		if (x == null) return;
		if (prefix.length() == pat.length() && x.val != null) q.add(prefix);
		if (prefix.length() == pat.length()) return;
		char next = pat.charAt(prefix.length());
		for (int c = 0; c < R; c++)
			if (next == '.' || next == c)
				collect(x.next[c], prefix + (char) c, pat, q);
	}

	public void delete(String key) {
		root = delete(root, key, 0);
	}

	private Node delete(Node x, String key, int d) {
		if (x == null) return null;
		if (d == key.length()) x.val = null;
		else {
			char c = key.charAt(d);
			x.next[c] = delete(x.next[c], key, d+1);
		}
		if (x.val != null) return x;
		for (int c = 0; c < R; c++)
			if (x.next[c] != null)
				return x;
		return null;
	}


	// test client
	public static void main(String[] args) {

		TrieST<String> st = new TrieST<String>();

		st.put("567", "Testing");

		System.out.println(st.longestPrefixOf("5671234"));

		for (String key : st.keys()) {
			System.out.println(key + " " + st.get(key));
		}
	}
}