• 数据结构 二叉平衡树 avl双旋转


    10,11,7,6,8,9

    package tree.bst.avl;
    
    public class AVLTreeDemo {
        public static void main(String[] args) {
            //int[] arr = {4,3,6,5,7,8};
            //int[] arr = {10,12,8,9,7,6};
            int[] arr = {10,11,7,6,8,9};
            AvlTree avlTree = new AvlTree();
    
            for (int i = 0; i < arr.length; i++) {
                avlTree.addNode(new Node(arr[i]));
            }
    
            // 中序遍历显示
            avlTree.infixOrder();
    
            // 求高度
            System.out.println(avlTree.getRoot().height());
            System.out.println(avlTree.getRoot().leftHeight());
            System.out.println(avlTree.getRoot().rightHeight());
    
            avlTree.infixOrder();
    
        }
    }
    
    class AvlTree {
        public Node getRoot() {
            return root;
        }
    
        public void setRoot(Node root) {
            this.root = root;
        }
    
        private Node root;
    
        public int height()
        {
            if (root == null){
                return 0;
            } else {
                return root.height();
            }
        }
    
        public void addNode(Node node) {
            if (root == null) {
                root = node;
            } else {
                root.add(node);
            }
        }
    
        public void infixOrder() {
            if (root == null) {
                return;
            }
    
            root.infixOrder();
        }
    
        public Node search(int value) {
            if (root == null) {
                return null;
            } else {
                return root.search(value);
            }
        }
    
        public Node searchParent(int value) {
            if (root == null) {
                return null;
            } else {
                return root.searchParent(value);
            }
        }
    
        /**
         * 删除最小节点
         *
         * @param node 传入的节点 当做一颗二叉排序书的根节点
         * @return 以node为根节点的的最小节点的值
         */
        public int delRightTreeMin(Node node) {
            Node temp = node;
    
            // 循环查找左子节点找到最小值
            while (temp.left != null) {
                temp = temp.left;
            }
    
            // delete the mini node
            deleteNode(temp.value);
    
            return temp.value;
        }
    
        public void deleteNode(int value) {
            if (root == null) {
                return;
            }
    
            // find thi node
            Node targetNode = this.search(value);
            // 如果没有找到要删除的节点
            if (targetNode == null) {
                return;
            }
    
            // 没有父节点
            if (root.left == null && root.right == null) {
                root = null;
                return;
            }
    
            Node parent = searchParent(value);
    
            //叶子节点
            if (targetNode.left == null && targetNode.right == null) {
                if (parent.left != null && parent.left.value == value) {
                    parent.left = null;
                } else if (parent.right != null && parent.right.value == value) {
                    parent.right = null;
                }
            } else if (targetNode.left != null && targetNode.right != null) { //两颗子树
                int min = this.delRightTreeMin(targetNode.right);
                targetNode.value = min;
            } else { // 一颗子树
                //  if has left node
    
                if (targetNode.left != null) {
                    if (parent != null) {
                        // 如果targetNode是parent的左右
                        if (parent.left.value == value) {
                            parent.left = targetNode.left;
                        } else {
                            parent.right = targetNode.left;
                        }
                    } else {
                        root = targetNode.left;
                    }
    
    
                } else {
                    if (parent != null) {
                        if (parent.right.value == value) {
                            parent.right = targetNode.right;
                        } else {
                            parent.left = targetNode.right;
                        }
                    } else {
                        root = targetNode.right;
                    }
    
                }
            }
        }
    
    }
    
    
    class Node {
        public int value;
        public Node left;
        public Node right;
    
        public Node(int value) {
            this.value = value;
        }
    
        public int leftHeight() {
            if (left == null) {
                return 0;
            } else {
                return left.height();
            }
        }
        // 左旋
        private void leftRotate()
        {
            //创建新的结点,以当前根结点的值
            Node newNode = new Node(value);
            //把新的结点的左子树设置成当前结点的左子树
            newNode.left = left;
            //把新的结点的右子树设置成带你过去结点的右子树的左子树
            newNode.right = right.left;
            //把当前结点的值替换成右子结点的值
            value = right.value;
            //把当前结点的右子树设置成当前结点右子树的右子树
            right = right.right;
            //把当前结点的左子树(左子结点)设置成新的结点
            left = newNode;
        }
    
        // 右旋
        private void rightRotate()
        {
            // 10  12 8 9 7 6 拿着转了玩
            Node newNode = new Node(value);
            newNode.right = right;
            newNode.left = left.right;
            value = left.value;
            left = left.left;
            right = newNode;
        }
    
        public int rightHeight() {
            if (right == null) {
                return 0;
            } else {
                return right.height();
            }
        }
    
        public int height() {
            return Math.max(this.left == null ? 0 : this.left.height(), this.right == null ? 0 : this.right.height()) + 1;
        }
    
        // find node
        public Node search(int value) {
            if (value == this.value) {
                return this;
            } else if (value < this.value) {
                // left tree find
                if (this.left == null) {
                    return null;
                }
                return this.left.search(value);
            } else {
                if (this.right == null) {
                    return null;
                }
    
                return this.right.search(value);
            }
    
        }
    
        // 查找要删除的节点的父节点
        public Node searchParent(int value) {
            if (this.left != null && this.left.value == value
                    || (this.right != null && this.right.value == value)) {
                return this;
            } else {
                if (value < this.value && this.left != null) {
                    return this.left.searchParent(value);
                } else if (value >= this.value && this.right != null) {
                    return this.right.searchParent(value);
                } else {
                    return null;
                }
            }
        }
    
        // 添加节点
        public void add(Node node) {
            if (node == null) {
                return;
            }
    
            // 添加 left
            if (node.value < this.value) {
                if (this.left == null) {
                    this.left = node;
                } else {
                    this.left.add(node);
                }
            }
    
            // 添加到right
            if (node.value > this.value) {
                if (this.right == null) {
                    this.right = node;
                } else {
                    this.right.add(node);
                }
            }
    
            // 添加完一个节点后 如果柚子树-左子树的高度>1 左旋转
            if(rightHeight() - leftHeight() > 1) {
                if(right!=null && right.leftHeight() > right.rightHeight()){
                    right.left.rightRotate();
                }
                leftRotate();
            } else if(leftHeight() - rightHeight() > 1) {
               if(left !=null && left.rightHeight() > left.leftHeight()){
                   left.leftRotate();
               }
               rightRotate();
            }
    
        }
    
        // 中序便利
        public void infixOrder() {
            if (this.left != null) {
                this.left.infixOrder();
            }
    
            System.out.println(this);
    
            if (this.right != null) {
                this.right.infixOrder();
            }
        }
    
        @Override
        public String toString() {
            return "Node{" +
                    "value=" + value +
                    '}';
        }
    }
    
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  • 原文地址:https://www.cnblogs.com/brady-wang/p/15148519.html
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