public 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;
//空參構造函數
public AVLTree(){
root = null;
size = 0;
}
publi int getSize(){
return size;
}
public boolean isEmpty(){
return size == 0;
}
/**************檢測是否符合AVLTree*********************/
//1. 檢測是否滿足二分搜索樹
//2. 檢測是否滿足節點平衡因子小於1
//檢查是否還是一顆二分搜索樹
//通過中序遍歷,是否滿足降序排列
public boolean isBST(){
ArrayList<K> keys = new ArrayList<>();
inOrder(root,key);
for(int i = 0;i < keys.size(); i++){
if(keys.get(i-1).compareTo(keys.get(i)>0{
return false;
}
}
}
private node inOrder(Node node, ArrayList<K> keys){
if(node == null){
return ;
}
inOrder(node.left, keys);
keys.add(node.key);
inOrder(node.right,key);
}
//判斷該二叉樹是否一顆平衡二叉樹
public boolean isBalanced() {
return isBalanced(root);
}
/*判斷node爲根的二叉樹是否是一顆二叉樹,遞歸算法*/
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);
}
//獲取node的高度
private int getHeight(Node node){
if(node == null){
return 0;
}
return node.height;
}
//獲取node的平衡因子
private int getBalanceFactor(Node node){
if(node == null){
return 0;
}
return getHeight(node.left) - getHeight(node.right);
}
/***************************************************************************************/
// 對節點y進行向右旋轉操作,返回旋轉後新的根節點x
// y x
// / \ / \
// x T4 向右旋轉 (y) z y
// / \ - - - - - - - -> / \ / \
// z T3 T1 T2 T3 T4
// / \
// T1 T2
private Node rightRotate (Node y){
Node x = y.left;
Node T3 = x.right;
//向右旋轉
x.left = y;
y.right = T3;
//維護高度
y.height = Math.max(getHeight(y.left),getHeight(y.right))+1;
x.height = Math.max(getHeight(x.left),getHeightx.right))+1;
return x;
}
// 對節點y進行向左旋轉操作,返回旋轉後新的根節點x
// y x
// / \ / \
// T1 x 向左旋轉 (y) y z
// / \ - - - - - - - -> / \ / \
// T2 z T1 T2 T3 T4
// / \
// T3 T4
private Node leftRotate(Node y) {
Node x = y.right;
Node T2 = x.left;
//向左旋轉過程
x.left = y;
y.right = T2;
//更新height; x;y節點的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;
}
//向二分搜索樹中添加新的元素
public void add (K key, V value){
root = add(root, key, value);
}
// 向以node爲根的二分搜索樹中插入元素(key, value),遞歸算法
// 返回插入新節點後二分搜索樹的根
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));
//計算平衡因子
int balanceFactory = getBalanceFactory(node);
//平衡維護
//LL
if(balanceFactory > 1 && getBalanceFactory(node.left) >= 0){
return rightRotate(node);
}
//RR
if(balanceFactory < -1 && getBalanceFactory(node.right) <= 0){
return leftRotate(node);
}
//LR
if(balanceFactory > 1 && getBalanceFactory(node.left) < 0){
//node.left進行左旋轉,轉化成LL型
node.left = leftRotate(node.left);
return rightRotate(node);
}
//RL
if(balanceFactory < -1 && getBalanceFactory(node.right) > 0){
//node.left進行左旋轉,轉化成RR型
node.right = leftRotate(node.right);
return leftRotate(node);
}
return node;
}
// 返回以node爲根節點的二分搜索樹中,key所在的節點
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);
}
}
//查找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爲根的二分搜索樹的最小值所在的節點
private Node minimum(Node node){
if(node.left == null){
return node;
}
return minim(node.left);
}
// 從二分搜索樹中刪除鍵爲key的節點
public V remove(K key) {
Node node = getNode(root, key);
if (node != null) {
root = remove(root, key);
return node.value;
}
return null;
}
//返回的節點是刪除節點後返回的二叉搜索樹的新的節點
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);
retNode = node;
} else if(key.compareTo(node.key) > 0)){
node.right = remove(node.right,key);
retNode = node;
}else{ // key.compareTo(node.key) == 0
//待刪除節點左子樹爲空的情況
if(node.left == null){
node.rightNode = node.right;
node.right = null;
size--;
retNode = rightNode;
}
//待刪除節點右子樹爲空的情況
else if(node.right == null){
Node leftNode = node.left;
node.left = null;
size --;
retNode = leftNode;
}
//待刪除節點左子樹均不爲空
//找到比該待刪除節點大的最小節點,即待刪除節點右子樹的最小節點
//用這個節點頂替待刪除節點的位置
else {
Node successor = minimum(node.right);
/*
successor.right = node.right;
*/
successor.right = remove(node.right,successor.key);
successor.left = node.left;
//爲了儘快回收
node.left = node.right = null;
retNode = successor
}
}
//判斷刪除節點是否是葉子節點,如果是葉子節點,直接返回
if (retNode == null) {
return null;
}
//更新height
retNode.height = 1 + Math.max(getHeight(retNode.left), getHeight(retNode.right));
// 計算平衡因子
int balanceFactory = getBalanceFactory(retNode);
// 平衡維護
// LL
if (balanceFactory > 1 && getBalanceFactory(retNode.left) >= 0) {
//當前節點平衡因子大於1,並且左孩子的平衡因子大於0,那麼右旋轉
return rightRotate(retNode);
}
//RR
if (balanceFactory < -1 && getBalanceFactory(retNode.right) <= 0) {
//當前節點平衡因子小於-1,並且左孩子的平衡因子小於0,那麼左旋轉
return leftRotate(retNode);
}
//LR
if (balanceFactory > 1 && getBalanceFactory(retNode.left) < 0) {
retNode.left = leftRotate(retNode.left);
return rightRotate(retNode);
}
//RL
if (balanceFactory < -1 && getBalanceFactory(retNode.right) > 0) {
retNode.right = rightRotate(retNode.right);
return leftRotate(retNode);
}
return retNode;
}
}
JAVA數據結構之AVLTree平衡二叉樹
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