平衡二叉树-java代码实现
资料引入说明
-
平衡二叉树理论知识参考:https://blog.csdn.net/dengjili/article/details/111463328
-
二叉排序树理论知识参考:https://blog.csdn.net/dengjili/article/details/111503799
-
二叉排序树-java代码实现:https://blog.csdn.net/dengjili/article/details/111992147
平衡二叉树是在二叉排序树代码基础上进行平衡的,这里直接使用了二叉排序树代码,本章节重点在于讲解平衡的过程
代码说明
定义节点如下,增加平衡因子,结点高度,指向父结点的引用三个属性
public class AVLNode {
private int value;
private AVLNode leftNode;
private AVLNode rightNode;
private int balanceFactor;
private int length;
private AVLNode parentNode;
// setter getter
采用层次遍历输出,便于观察使用,输出结点信息
public class AVLLevelTraversal {
public static void traversal(AVLNode AVLNode) {
System.out.println("----------------------");
Queue<AVLNode> queue = new LinkedBlockingDeque<>();
queue.add(AVLNode);
while (!queue.isEmpty()) {
AVLNode pollNode = queue.poll();
System.out.println(String.format("value=%s, length=%s, balanceFactor=%s", pollNode.getValue(), pollNode.getLength(), pollNode.getBalanceFactor()));
AVLNode leftNode = pollNode.getLeftNode();
if (leftNode != null) {
queue.add(leftNode);
}
AVLNode rightNode = pollNode.getRightNode();
if (rightNode != null) {
queue.add(rightNode);
}
}
}
}
平衡二叉树增加实现,其中复用了二叉排序树功能,新增的单独标注
public class AVLTree {
/** ================================================*/
/** 二叉树排序功能 开始 */
/** ================================================*/
public static AVLNode insert(AVLNode AVLNode, int value) {
if (AVLNode == null) {
AVLNode = new AVLNode(value);
} else {
int currentValue = AVLNode.getValue();
if (currentValue > value) {
AVLNode leftAVLNode = AVLNode.getLeftNode();
leftAVLNode = insert(leftAVLNode, value);
AVLNode.setLeftNode(leftAVLNode);
leftAVLNode.setParentNode(AVLNode);
} else if (currentValue < value) {
AVLNode rightAVLNode = AVLNode.getRightNode();
rightAVLNode = insert(rightAVLNode, value);
AVLNode.setRightNode(rightAVLNode);
rightAVLNode.setParentNode(AVLNode);
}
// don't deal with currentValue equals with value
}
return AVLNode;
}
public static AVLNode delete(AVLNode root, int value) {
AVLNode isExistAVLNode = search(root, value);
if (isExistAVLNode == null) {
return root;
}
// 标记待删除节点的父结点,其中若删除的是根节点,则parentAVLNode为空
AVLNode parentAVLNode = null;
AVLNode currentAVLNode = root;
while (currentAVLNode != null && currentAVLNode.getValue() != value) {
parentAVLNode = currentAVLNode;
if (currentAVLNode.getValue() > value) {
currentAVLNode = currentAVLNode.getLeftNode();
} else {
currentAVLNode = currentAVLNode.getRightNode();
}
}
// 删除,分三种情况处理
// 1. 叶子节点
if (currentAVLNode.getLeftNode() == null && currentAVLNode.getRightNode() == null) {
if (parentAVLNode != null) {
if (parentAVLNode.getValue() > value) {
parentAVLNode.setLeftNode(null);
} else {
parentAVLNode.setRightNode(null);
}
} else {
root = null;
}
}
// 2. 只存在一个子节点
else if (currentAVLNode.getLeftNode() == null && currentAVLNode.getRightNode() != null) {
if (parentAVLNode != null) {
if (parentAVLNode.getValue() > value) {
parentAVLNode.setLeftNode(currentAVLNode.getRightNode());
} else {
parentAVLNode.setRightNode(currentAVLNode.getRightNode());
}
} else {
root = currentAVLNode.getRightNode();
}
}
else if (currentAVLNode.getLeftNode() != null && currentAVLNode.getRightNode() == null) {
if (parentAVLNode != null) {
if (parentAVLNode.getValue() > value) {
parentAVLNode.setLeftNode(currentAVLNode.getLeftNode());
} else {
parentAVLNode.setRightNode(currentAVLNode.getLeftNode());
}
} else {
root = currentAVLNode.getLeftNode();
}
}
// 3. 存在两个子节点(采用替代法-可重用代码:找出被删除节点的右子树,找出最大的结点,替换被删除的结点)
else if (currentAVLNode.getLeftNode() != null && currentAVLNode.getRightNode() != null) {
// 3.1 找出右子树最大节点
AVLNode currentMinAVLNode = currentAVLNode;
while (currentMinAVLNode.getLeftNode() != null) {
currentMinAVLNode = currentMinAVLNode.getLeftNode();
}
// 3.2 删除右子树最大节点
root = delete(root, currentMinAVLNode.getValue());
// 3.3 替换待删除节点
currentMinAVLNode.setLeftNode(currentAVLNode.getLeftNode());
currentMinAVLNode.setRightNode(currentAVLNode.getRightNode());
// 3.4 设置父结点子引用
if (parentAVLNode != null) {
if (parentAVLNode.getValue() > value) {
parentAVLNode.setLeftNode(currentMinAVLNode);
} else {
parentAVLNode.setRightNode(currentMinAVLNode);
}
} else {
root = currentMinAVLNode;
}
}
return root;
}
public static AVLNode search(AVLNode AVLNode, int value) {
if (AVLNode == null) {
return null;
}
int currentValue = AVLNode.getValue();
if (value == currentValue) {
return AVLNode;
} else if (currentValue > value) {
AVLNode leftAVLNode = AVLNode.getLeftNode();
return search(leftAVLNode, value);
} else {
AVLNode rightAVLNode = AVLNode.getRightNode();
return search(rightAVLNode, value);
}
}
public static AVLNode search2(AVLNode AVLNode, int value) {
AVLNode currentAVLNode = AVLNode;
while (currentAVLNode != null) {
int currentValue = currentAVLNode.getValue();
if (value == currentValue) {
return currentAVLNode;
} else if (currentValue > value) {
currentAVLNode = currentAVLNode.getLeftNode();
} else {
currentAVLNode = currentAVLNode.getRightNode();
}
}
return null;
}
public static AVLNode createBST(int[] nums) {
AVLNode root = null;
for (int value : nums) {
root = insert(root, value);
}
return root;
}
/** ================================================*/
/** 二叉树排序功能 结束 */
/** ================================================*/
// ==================================================//
/** ================================================*/
/** 平衡二叉树功能 开始 */
/** ================================================*/
public static AVLNode createAVL(int[] nums) {
AVLNode root = null;
for (int value : nums) {
root = insertAVL(root, value);
}
return root;
}
public static AVLNode insertAVL(AVLNode AVLNode, int value) {
// 复用原二叉排序树功能
AVLNode root = insert(AVLNode, value);
// 计算平衡影子
resetBalanceFactor(root);
// 平衡
root = rebalance(root);
return root;
}
/**
* <p>Description: 核心平衡方法</p>
*/
private static AVLNode rebalance(AVLNode root) {
// 判断树是否满足平衡二叉树,不是平衡二叉树返回非平衡结点
AVLNode nonAVLNode = getNonAVLNode(root);
while (nonAVLNode != null) {
// 找出调整结点
AVLRotate aVLRotate = new RoutingAVLRotate();
AVLNode rootAVLSubTree = aVLRotate.rotate(nonAVLNode);
// 判断旋转结点是否为原根节点
if (rootAVLSubTree.getParentNode() == null) {
root = rootAVLSubTree;
}
resetBalanceFactor(root);
// redo
nonAVLNode = getNonAVLNode(root);
}
return root;
}
private static void resetBalanceFactor(AVLNode AVLNode) {
AVLNode leftNode = AVLNode.getLeftNode();
AVLNode rightNode = AVLNode.getRightNode();
int leftAVLNodeLength = 0;
if (leftNode != null) {
resetBalanceFactor(leftNode);
leftAVLNodeLength = leftNode.getLength();
}
int rightAVLNodeLength = 0;
if (rightNode != null) {
resetBalanceFactor(rightNode);
rightAVLNodeLength = rightNode.getLength();
}
// 根据左右子树的的高度计算节点的高度、平衡因子
int AVLNodeLength = Math.max(leftAVLNodeLength, rightAVLNodeLength) + 1;
int AVLNodeBalanceFactor = leftAVLNodeLength - rightAVLNodeLength;
AVLNode.setLength(AVLNodeLength);
AVLNode.setBalanceFactor(AVLNodeBalanceFactor);
}
/**
* <p>Description: 遍历搜索所有结点是否满足平衡二叉树-[通用]</p>
*/
private static AVLNode getNonAVLNode(AVLNode node) {
AVLNode nonAVLNode = null;
// 使用层次遍历,找出平衡因子为+-2的结点
Queue<AVLNode> queue = new LinkedBlockingDeque<>();
queue.add(node);
while (!queue.isEmpty()) {
AVLNode pollNode = queue.poll();
int balanceFactor = pollNode.getBalanceFactor();
if (balanceFactor > 1 || balanceFactor < -1) {
nonAVLNode = pollNode;
break;
}
AVLNode leftNode = pollNode.getLeftNode();
if (leftNode != null) {
queue.add(leftNode);
}
AVLNode rightNode = pollNode.getRightNode();
if (rightNode != null) {
queue.add(rightNode);
}
}
return nonAVLNode;
}
/** ================================================*/
/** 平衡二叉树功能 结束 */
/** ================================================*/
}
核心平衡代码,这里抽象为单独的几个类实现
AVLRotate aVLRotate = new RoutingAVLRotate();
AVLNode rootAVLSubTree = aVLRotate.rotate(nonAVLNode);
平衡接口定义
public interface AVLRotate {
AVLNode rotate(AVLNode rotateNode);
}
平衡路由选择
public class RoutingAVLRotate implements AVLRotate {
@Override
public AVLNode rotate(AVLNode rotateNode) {
AVLRotate aVLRotate = null;
if (rotateNode.getBalanceFactor() > 0) {
AVLNode leftNode = rotateNode.getLeftNode();
if (leftNode.getBalanceFactor() > 0) {
// LL
aVLRotate = new LLAVLRotate();
} else {
// LR
aVLRotate = new LRAVLRotate();
}
} else {
AVLNode rightNode = rotateNode.getRightNode();
if (rightNode.getBalanceFactor() > 0) {
// RL
aVLRotate = new RLAVLRotate();
} else {
// RR
aVLRotate = new RRAVLRotate();
}
}
AVLNode rootAVLSubTree = aVLRotate.rotate(rotateNode);
return rootAVLSubTree;
}
}
LL实现
public class LLAVLRotate implements AVLRotate {
@Override
public AVLNode rotate(AVLNode rotateNode) {
AVLNode rootAVLSubTree = rotateNode.getLeftNode();
int value = rotateNode.getValue();
AVLNode parentNode = rotateNode.getParentNode();
rootAVLSubTree.setParentNode(parentNode);
if (parentNode != null) {
if (parentNode.getValue() > value) {
parentNode.setLeftNode(rootAVLSubTree);
} else {
parentNode.setRightNode(rootAVLSubTree);
}
}
// 调整
rotateNode.setLeftNode(rootAVLSubTree.getRightNode());
rootAVLSubTree.setRightNode(rotateNode);
rotateNode.setParentNode(rootAVLSubTree);
return rootAVLSubTree;
}
}
LR实现
public class LRAVLRotate implements AVLRotate {
@Override
public AVLNode rotate(AVLNode rotateNode) {
AVLNode leftNode = rotateNode.getLeftNode();
AVLNode rootAVLSubTree = leftNode.getRightNode();
int value = rotateNode.getValue();
AVLNode parentNode = rotateNode.getParentNode();
rootAVLSubTree.setParentNode(parentNode);
if (parentNode != null) {
if (parentNode.getValue() > value) {
parentNode.setLeftNode(rootAVLSubTree);
} else {
parentNode.setRightNode(rootAVLSubTree);
}
}
// 调整
leftNode.setRightNode(rootAVLSubTree.getLeftNode());
rotateNode.setLeftNode(rootAVLSubTree.getRightNode());
rootAVLSubTree.setLeftNode(leftNode);
rootAVLSubTree.setRightNode(rotateNode);
rotateNode.setParentNode(rootAVLSubTree);
leftNode.setParentNode(rootAVLSubTree);
return rootAVLSubTree;
}
}
RL实现
public class RLAVLRotate implements AVLRotate {
@Override
public AVLNode rotate(AVLNode rotateNode) {
AVLNode rightNode = rotateNode.getRightNode();
AVLNode rootAVLSubTree = rightNode.getLeftNode();
int value = rotateNode.getValue();
AVLNode parentNode = rotateNode.getParentNode();
rootAVLSubTree.setParentNode(parentNode);
if (parentNode != null) {
if (parentNode.getValue() > value) {
parentNode.setLeftNode(rootAVLSubTree);
} else {
parentNode.setRightNode(rootAVLSubTree);
}
}
// 调整
rightNode.setLeftNode(rootAVLSubTree.getRightNode());
rotateNode.setRightNode(rootAVLSubTree.getLeftNode());
rootAVLSubTree.setLeftNode(rotateNode);
rootAVLSubTree.setRightNode(rightNode);
rotateNode.setParentNode(rootAVLSubTree);
rightNode.setParentNode(rootAVLSubTree);
return rootAVLSubTree;
}
}
RR实现
public class RRAVLRotate implements AVLRotate {
@Override
public AVLNode rotate(AVLNode rotateNode) {
AVLNode rootAVLSubTree = rotateNode.getRightNode();
int value = rotateNode.getValue();
AVLNode parentNode = rotateNode.getParentNode();
rootAVLSubTree.setParentNode(parentNode);
if (parentNode != null) {
if (parentNode.getValue() > value) {
parentNode.setLeftNode(rootAVLSubTree);
} else {
parentNode.setRightNode(rootAVLSubTree);
}
}
// 调整
rotateNode.setRightNode(rootAVLSubTree.getLeftNode());
rootAVLSubTree.setLeftNode(rotateNode);
rotateNode.setParentNode(rootAVLSubTree);
return rootAVLSubTree;
}
}
测试类
public class AVLTreeTest6 {
public static void main(String[] args) {
int nums[] = { 4, 1, 2, 5, 0, 7, 9, 8, 3, 6 };
AVLNode tree = AVLTree.createAVL(nums);
AVLLevelTraversal.traversal(tree);
}
}
输出结果
----------------------
value=5, length=4, balanceFactor=0
value=2, length=3, balanceFactor=0
value=8, length=3, balanceFactor=1
value=1, length=2, balanceFactor=1
value=4, length=2, balanceFactor=1
value=7, length=2, balanceFactor=1
value=9, length=1, balanceFactor=0
value=0, length=1, balanceFactor=0
value=3, length=1, balanceFactor=0
value=6, length=1, balanceFactor=0
推理过程{ 4, 1, 2, 5, 0, 7, 9, 8, 3, 6 }
- { 1, 2, 5, 0, 7, 9, 8, 3, 6 } -> 4
4
- { 2, 5, 0, 7, 9, 8, 3, 6 } -> 1
4
/
1
- { 5, 0, 7, 9, 8, 3, 6 } -> 2
4
/
1
\
2
LR旋转
(412)
2
/ \
1 4
- { 0, 7, 9, 8, 3, 6 } -> 5
2
/ \
1 4
\
5
- { 7, 9, 8, 3, 6 } -> 0
2
/ \
1 4
/ \
0 5
- { 9, 8, 3, 6 } -> 7
2
/ \
1 4
/ \
0 5
\
7
RR旋转
(457)
2
/ \
1 5
/ / \
0 4 7
- { 8, 3, 6 } -> 9
2
/ \
1 5
/ / \
0 4 7
\
9
- { 3, 6 } -> 8
2
/ \
1 5
/ / \
0 4 7
\
9
/
8
RR旋转
(257)
5
/ \
2 7
/ \ \
1 4 9
/ /
0 8
RL旋转
(798)
5
/ \
2 8
/ \ / \
1 4 7 9
/
0
- { 6 } -> 3
5
/ \
2 8
/ \ / \
1 4 7 9
/ /
0 3
- { } -> 6
5
/ \
2 8
/ \ / \
1 4 7 9
/ / /
0 3 6
层序遍历结果对比-一致
----------------------
value=5, length=4, balanceFactor=0
value=2, length=3, balanceFactor=0
value=8, length=3, balanceFactor=1
value=1, length=2, balanceFactor=1
value=4, length=2, balanceFactor=1
value=7, length=2, balanceFactor=1
value=9, length=1, balanceFactor=0
value=0, length=1, balanceFactor=0
value=3, length=1, balanceFactor=0
value=6, length=1, balanceFactor=0
核心代码说明,并轻松实现平衡二叉树删除功能
插入方法
public static AVLNode insertAVL(AVLNode AVLNode, int value) {
// 复用原二叉排序树功能
AVLNode root = insert(AVLNode, value);
// 计算平衡影子
resetBalanceFactor(root);
// 平衡
root = rebalance(root);
return root;
}
我们可以注意到,核心方法是root = rebalance(root);
方法,实现了平衡,那么我们如果实现删除后平衡如何实现,非常简单,即
public static AVLNode deleteAVL(AVLNode AVLNode, int value) {
// 复用原二叉排序树功能
AVLNode root = delete(AVLNode, value);
// 计算平衡影子
resetBalanceFactor(root);
// 平衡
root = rebalance(root);
return root;
}
测试在原有基础上删除9
5
/ \
2 8
/ \ / \
1 4 7 9
/ / /
0 3 6
二叉排序树删除变化后
5
/ \
2 8
/ \ /
1 4 7
/ / /
0 3 6
平衡旋转(LL旋转)
5
/ \
2 7
/ \ / \
1 4 6 8
/ /
0 3
测试类
public class AVLTreeTest {
public static void main(String[] args) {
int nums[] = { 4, 1, 2, 5, 0, 7, 9, 8, 3, 6 };
AVLNode tree = AVLTree.createAVL(nums);
AVLLevelTraversal.traversal(tree);
AVLNode deleteTree = AVLTree.delete(tree, 9);
AVLLevelTraversal.traversal(deleteTree);
}
}
输出,预期一致
----------------------
value=5, length=4, balanceFactor=1
value=2, length=3, balanceFactor=0
value=7, length=2, balanceFactor=0
value=1, length=2, balanceFactor=1
value=4, length=2, balanceFactor=1
value=6, length=1, balanceFactor=0
value=8, length=1, balanceFactor=0
value=0, length=1, balanceFactor=0
value=3, length=1, balanceFactor=0
当然,这个原二叉排序树删除逻辑有点问题,删除节点后,还需要设置AVLNode节点的parentNode引用,这是因为我们是从二叉排序树过渡来的,修改删除代码public static AVLNode delete(AVLNode root, int value)
;
添加三次设置父对象引入即可,分别是
- currentAVLNode.getRightNode().setParentNode(parentAVLNode);
- currentAVLNode.getLeftNode().setParentNode(parentAVLNode);
- currentMinAVLNode.setParentNode(parentAVLNode);
public static AVLNode delete(AVLNode root, int value) {
AVLNode isExistAVLNode = search(root, value);
if (isExistAVLNode == null) {
return root;
}
// 标记待删除节点的父结点,其中若删除的是根节点,则parentAVLNode为空
AVLNode parentAVLNode = null;
AVLNode currentAVLNode = root;
while (currentAVLNode != null && currentAVLNode.getValue() != value) {
parentAVLNode = currentAVLNode;
if (currentAVLNode.getValue() > value) {
currentAVLNode = currentAVLNode.getLeftNode();
} else {
currentAVLNode = currentAVLNode.getRightNode();
}
}
// 删除,分三种情况处理
// 1. 叶子节点
if (currentAVLNode.getLeftNode() == null && currentAVLNode.getRightNode() == null) {
if (parentAVLNode != null) {
if (parentAVLNode.getValue() > value) {
parentAVLNode.setLeftNode(null);
} else {
parentAVLNode.setRightNode(null);
}
} else {
root = null;
}
}
// 2. 只存在一个子节点
else if (currentAVLNode.getLeftNode() == null && currentAVLNode.getRightNode() != null) {
if (parentAVLNode != null) {
if (parentAVLNode.getValue() > value) {
parentAVLNode.setLeftNode(currentAVLNode.getRightNode());
} else {
parentAVLNode.setRightNode(currentAVLNode.getRightNode());
}
} else {
root = currentAVLNode.getRightNode();
}
currentAVLNode.getRightNode().setParentNode(parentAVLNode);
}
else if (currentAVLNode.getLeftNode() != null && currentAVLNode.getRightNode() == null) {
if (parentAVLNode != null) {
if (parentAVLNode.getValue() > value) {
parentAVLNode.setLeftNode(currentAVLNode.getLeftNode());
} else {
parentAVLNode.setRightNode(currentAVLNode.getLeftNode());
}
} else {
root = currentAVLNode.getLeftNode();
}
currentAVLNode.getLeftNode().setParentNode(parentAVLNode);
}
// 3. 存在两个子节点(采用替代法-可重用代码:找出被删除节点的右子树,找出最大的结点,替换被删除的结点)
else if (currentAVLNode.getLeftNode() != null && currentAVLNode.getRightNode() != null) {
// 3.1 找出右子树最大节点
AVLNode currentMinAVLNode = currentAVLNode.getRightNode();
while (currentMinAVLNode.getLeftNode() != null) {
currentMinAVLNode = currentMinAVLNode.getLeftNode();
}
// 3.2 删除右子树最大节点
root = delete(root, currentMinAVLNode.getValue());
// 3.3 替换待删除节点
currentMinAVLNode.setLeftNode(currentAVLNode.getLeftNode());
currentMinAVLNode.setRightNode(currentAVLNode.getRightNode());
// 3.4 设置父结点子引用
if (parentAVLNode != null) {
if (parentAVLNode.getValue() > value) {
parentAVLNode.setLeftNode(currentMinAVLNode);
} else {
parentAVLNode.setRightNode(currentMinAVLNode);
}
} else {
root = currentMinAVLNode;
}
currentMinAVLNode.setParentNode(parentAVLNode);
}
return root;
}
请自行验证
到这里就完成了平衡功能,接下来我们将学习红黑树
本文地址:https://blog.csdn.net/dengjili/article/details/112851332