下面的代码实现了对红黑树的元素的添加和查找,想要了解和掌握,就要先理解2-3树的思想.红黑二叉查找树的思想是用将3-结点表示为由一条左斜的红色链接(两个2-结点其中之一是另一个左子结点)相连的两个2-结点,而且,我们无需修改就可以直接使用标准二叉查找树的表示方法

package cn.edu.zzuli.api;

import cn.edu.zzuli.api.BST;
import edu.princeton.cs.algs4.StdIn;
import edu.princeton.cs.algs4.StdOut;

public class RedBlackBST<Key extends Comparable<Key>, Value>{
	private static final boolean RED = true;
	private static final boolean BLACK = false;
	private Node root;
	private class Node{
		Key key;//键
		Value val;//相关联的值
		int N;//这棵子树中的结点总数
		Node left, right;//左右子树
		boolean color;//由其父结点指向它的链接的颜色
		public Node(Key key, Value val, int N, boolean color) {
			this.key = key;
			this.val = val;
			this.N = N;
			this.color = color;
		}
	}
	//如果指向它的链接是红色的,那么该变量为true,黑色则为false.
	//约定空链接为黑色
	private boolean isRed(Node h) {
		if(h == null)
			return false;
		return h.color == RED;
	}
	//左旋转
	private Node rotateLeft(Node h) {
		Node x = h.right;
		h.right = x.left;
		x.left = h;
		x.color = h.color;
		h.color = RED;
		x.N = h.N;
		h.N = 1 + size(h.left) + size(h.right);
		return x;
	}
	//右旋转
	private Node rotateRight(Node h) {
		Node x = h.left;
		h.left = x.right;
		x.right = h;
		x.color = h.color;
		h.color = RED;
		x.N = h.N;
		h.N = 1 + size(h.left) + size(h.right);
		return x;
	}
	//转换一个结点的两个红色子结点的颜色
	//除了将子结点的颜色从红变黑外,还要将父节点的颜色从黑变红
	private void flipColors1(Node h) {
		h.color = RED;
		h.left.color = BLACK;
		h.right.color = BLACK;
	}
	//这棵子树中的结点总数
	public int size() {
		return size(root);
	}
	private int size(Node x) {
		if (x == null)
			return 0;
		else
			return x.N;
	}
	public void put(Key key, Value val) {
		//查找key,找到则更新其值,否则为它新建一个结点
		root = put(root, key, val);
		//每次插入后都会将根结点设为黑色
		root.color = BLACK;
	}
	private Node put(Node h, Key key, Value val) {
		if(h == null)//标准的插入操作,和父结点用红链接相连
			return new Node(key, val, 1, RED);
		int cmp = key.compareTo(h.key);
		if(cmp < 0) {
			h.left = put(h.left, key, val);
		}else if(cmp > 0) {
			h.right = put(h.right, key, val);
		}else {
			h.val = val;
		}
		//如果右子结点是红色的而左子结点是黑色的,进行左旋转
		if(!isRed(h.left) && isRed(h.right)) {
			h = rotateLeft(h);
		}
		//如果左子结点是红色的且它的左子结点也是红色的,进行右旋转
		if(isRed(h.left) && isRed(h.left.left)) {
			h = rotateRight(h);
		}
		//如果左右子结点均为红色,进行颜色转换
		if(isRed(h.left) && isRed(h.right)) {
			flipColors1(h);
		}
		h.N = 1 + size(h.left) + size(h.right);
		return h;
	}
	
	public Value get(Key key) {
		return get(root, key).val;
	}
	private Node get(Node h, Key key) {
		if(h == null)
			return null;
		int cmp = key.compareTo(h.key);
		if(cmp < 0) {
			return get(h.left, key);
		}else if(cmp > 0) {
			return get(h.right, key);
		}
		return h;
	}
	public static void main(String[] args) { 
        RedBlackBST<String, Integer> st = new RedBlackBST<String, Integer>();
        for (int i = 0; !StdIn.isEmpty(); i++) {
            String key = StdIn.readString();
            st.put(key, i);
        }
        //for (String s : st.keys())
            StdOut.println(st.get("A"));
        StdOut.println();
    }
}