Solution350.java

/// Leetcode 350. Intersection of Two Arrays II
/// https://leetcode.com/problems/intersection-of-two-arrays-ii/description/

import java.util.ArrayList;

public class Solution350 {

    private class AVLTree<K extends Comparable<K>, V> {

        private class Node{
            public K key;
            public V value;
            public Node left, right;
            public int height;

            public Node(K key, V value){
                this.key = key;
                this.value = value;
                left = null;
                right = null;
                height = 1;
            }
        }

        private Node root;
        private int size;

        public AVLTree(){
            root = null;
            size = 0;
        }

        public int getSize(){
            return size;
        }

        public boolean isEmpty(){
            return size == 0;
        }

        // 判断该二叉树是否是一棵二分搜索树
        public boolean isBST(){

            ArrayList<K> keys = new ArrayList<>();
            inOrder(root, keys);
            for(int i = 1 ; i < keys.size() ; i ++)
                if(keys.get(i - 1).compareTo(keys.get(i)) > 0)
                    return false;
            return true;
        }

        private void inOrder(Node node, ArrayList<K> keys){

            if(node == null)
                return;

            inOrder(node.left, keys);
            keys.add(node.key);
            inOrder(node.right, keys);
        }

        // 判断该二叉树是否是一棵平衡二叉树
        public boolean isBalanced(){
            return isBalanced(root);
        }

        // 判断以Node为根的二叉树是否是一棵平衡二叉树，递归算法
        private boolean isBalanced(Node node){

            if(node == null)
                return true;

            int balanceFactor = getBalanceFactor(node);
            if(Math.abs(balanceFactor) > 1)
                return false;
            return isBalanced(node.left) && isBalanced(node.right);
        }

        // 获得节点node的高度
        private int getHeight(Node node){
            if(node == null)
                return 0;
            return node.height;
        }

        // 获得节点node的平衡因子
        private int getBalanceFactor(Node node){
            if(node == null)
                return 0;
            return getHeight(node.left) - getHeight(node.right);
        }

        // 对节点y进行向右旋转操作，返回旋转后新的根节点x
        //        y                              x
        //       / \                           /   \
        //      x   T4     向右旋转 (y)        z     y
        //     / \       - - - - - - - ->    / \   / \
        //    z   T3                       T1  T2 T3 T4
        //   / \
        // T1   T2
        private Node rightRotate(Node y) {
            Node x = y.left;
            Node T3 = x.right;

            // 向右旋转过程
            x.right = y;
            y.left = T3;

            // 更新height
            y.height = Math.max(getHeight(y.left), getHeight(y.right)) + 1;
            x.height = Math.max(getHeight(x.left), getHeight(x.right)) + 1;

            return x;
        }

        // 对节点y进行向左旋转操作，返回旋转后新的根节点x
        //    y                             x
        //  /  \                          /   \
        // T1   x      向左旋转 (y)       y     z
        //     / \   - - - - - - - ->   / \   / \
        //   T2  z                     T1 T2 T3 T4
        //      / \
        //     T3 T4
        private Node leftRotate(Node y) {
            Node x = y.right;
            Node T2 = x.left;

            // 向左旋转过程
            x.left = y;
            y.right = T2;

            // 更新height
            y.height = Math.max(getHeight(y.left), getHeight(y.right)) + 1;
            x.height = Math.max(getHeight(x.left), getHeight(x.right)) + 1;

            return x;
        }

        // 向二分搜索树中添加新的元素(key, value)
        public void add(K key, V value){
            root = add(root, key, value);
        }

        // 向以node为根的二分搜索树中插入元素(key, value)，递归算法
        // 返回插入新节点后二分搜索树的根
        private Node add(Node node, K key, V value){

            if(node == null){
                size ++;
                return new Node(key, value);
            }

            if(key.compareTo(node.key) < 0)
                node.left = add(node.left, key, value);
            else if(key.compareTo(node.key) > 0)
                node.right = add(node.right, key, value);
            else // key.compareTo(node.key) == 0
                node.value = value;

            // 更新height
            node.height = 1 + Math.max(getHeight(node.left), getHeight(node.right));

            // 计算平衡因子
            int balanceFactor = getBalanceFactor(node);

            // 平衡维护
            // LL
            if (balanceFactor > 1 && getBalanceFactor(node.left) >= 0)
                return rightRotate(node);

            // RR
            if (balanceFactor < -1 && getBalanceFactor(node.right) <= 0)
                return leftRotate(node);

            // LR
            if (balanceFactor > 1 && getBalanceFactor(node.left) < 0) {
                node.left = leftRotate(node.left);
                return rightRotate(node);
            }

            // RL
            if (balanceFactor < -1 && getBalanceFactor(node.right) > 0) {
                node.right = rightRotate(node.right);
                return leftRotate(node);
            }

            return node;
        }

        // 返回以node为根节点的二分搜索树中，key所在的节点
        private Node getNode(Node node, K key){

            if(node == null)
                return null;

            if(key.equals(node.key))
                return node;
            else if(key.compareTo(node.key) < 0)
                return getNode(node.left, key);
            else // if(key.compareTo(node.key) > 0)
                return getNode(node.right, key);
        }

        public boolean contains(K key){
            return getNode(root, key) != null;
        }

        public V get(K key){

            Node node = getNode(root, key);
            return node == null ? null : node.value;
        }

        public void set(K key, V newValue){
            Node node = getNode(root, key);
            if(node == null)
                throw new IllegalArgumentException(key + " doesn't exist!");

            node.value = newValue;
        }

        // 返回以node为根的二分搜索树的最小值所在的节点
        private Node minimum(Node node){
            if(node.left == null)
                return node;
            return minimum(node.left);
        }

        // 从二分搜索树中删除键为key的节点
        public V remove(K key){

            Node node = getNode(root, key);
            if(node != null){
                root = remove(root, key);
                return node.value;
            }
            return null;
        }

        private Node remove(Node node, K key){

            if( node == null )
                return null;

            Node retNode;
            if( key.compareTo(node.key) < 0 ){
                node.left = remove(node.left , key);
                // return node;
                retNode = node;
            }
            else if(key.compareTo(node.key) > 0 ){
                node.right = remove(node.right, key);
                // return node;
                retNode = node;
            }
            else{   // key.compareTo(node.key) == 0

                // 待删除节点左子树为空的情况
                if(node.left == null){
                    Node rightNode = node.right;
                    node.right = null;
                    size --;
                    // return rightNode;
                    retNode = rightNode;
                }

                // 待删除节点右子树为空的情况
                else if(node.right == null){
                    Node leftNode = node.left;
                    node.left = null;
                    size --;
                    // return leftNode;
                    retNode = leftNode;
                }

                // 待删除节点左右子树均不为空的情况
                else{
                    // 找到比待删除节点大的最小节点, 即待删除节点右子树的最小节点
                    // 用这个节点顶替待删除节点的位置
                    Node successor = minimum(node.right);
                    //successor.right = removeMin(node.right);
                    successor.right = remove(node.right, successor.key);
                    successor.left = node.left;

                    node.left = node.right = null;

                    // return successor;
                    retNode = successor;
                }
            }

            if(retNode == null)
                return null;

            // 更新height
            retNode.height = 1 + Math.max(getHeight(retNode.left), getHeight(retNode.right));

            // 计算平衡因子
            int balanceFactor = getBalanceFactor(retNode);

            // 平衡维护
            // LL
            if (balanceFactor > 1 && getBalanceFactor(retNode.left) >= 0)
                return rightRotate(retNode);

            // RR
            if (balanceFactor < -1 && getBalanceFactor(retNode.right) <= 0)
                return leftRotate(retNode);

            // LR
            if (balanceFactor > 1 && getBalanceFactor(retNode.left) < 0) {
                retNode.left = leftRotate(retNode.left);
                return rightRotate(retNode);
            }

            // RL
            if (balanceFactor < -1 && getBalanceFactor(retNode.right) > 0) {
                retNode.right = rightRotate(retNode.right);
                return leftRotate(retNode);
            }

            return retNode;
        }

    }

    private interface Map<K, V> {

        void add(K key, V value);
        boolean contains(K key);
        V get(K key);
        void set(K key, V newValue);
        V remove(K key);
        int getSize();
        boolean isEmpty();
    }

    private class AVLMap<K extends Comparable<K>, V> implements Map<K, V> {

        private AVLTree<K, V> avl;

        public AVLMap(){
            avl = new AVLTree<>();
        }

        @Override
        public int getSize(){
            return avl.getSize();
        }

        @Override
        public boolean isEmpty(){
            return avl.isEmpty();
        }

        @Override
        public void add(K key, V value){
            avl.add(key, value);
        }

        @Override
        public boolean contains(K key){
            return avl.contains(key);
        }

        @Override
        public V get(K key){
            return avl.get(key);
        }

        @Override
        public void set(K key, V newValue){
            avl.set(key, newValue);
        }

        @Override
        public V remove(K key){
            return avl.remove(key);
        }
    }

    public int[] intersect(int[] nums1, int[] nums2) {

        AVLMap<Integer, Integer> map = new AVLMap<>();
        for(int num: nums1){
            if(!map.contains(num))
                map.add(num, 1);
            else
                map.add(num, map.get(num) + 1);
        }

        ArrayList<Integer> res = new ArrayList<>();
        for(int num: nums2){
            if(map.contains(num)){
                res.add(num);
                map.add(num, map.get(num) - 1);
                if(map.get(num) == 0)
                    map.remove(num);
            }
        }

        int[] ret = new int[res.size()];
        for(int i = 0 ; i < res.size() ; i ++)
            ret[i] = res.get(i);

        return ret;
    }
}