• 数据结构 bst二叉排序树 节点删除


    删除叶子节点
    删除只有一个的子节点的
    删除有两个子节点的

    package tree.bst;
    
    public class bstDemo {
        public static void main(String[] args) {
            System.out.println("二叉排序树");
    
            BstTree bstTree = new BstTree();
    
            int[] arr = {7, 3, 10, 12, 5, 1, 9, 2};
            for (int i = 0; i < arr.length; i++) {
                bstTree.addNode(new Node(arr[i]));
            }
    
            //bstTree.infixOrder();
    
            // 删除叶子节点
    //        bstTree.deleteNode(12);
    //        System.out.println("删除后");
    //        bstTree.infixOrder();
    
    //        // delete 一颗子树的节点
    //        bstTree.deleteNode(1);
    //        bstTree.infixOrder();
    
            // delete 2颗子树的节点
            bstTree.deleteNode(2);
            bstTree.deleteNode(5);
            bstTree.deleteNode(9);
            bstTree.deleteNode(12);
            bstTree.deleteNode(7);
            bstTree.deleteNode(3);
            bstTree.deleteNode(10);
            bstTree.deleteNode(1);
    
            bstTree.infixOrder();
    
        }
    }
    
    class BstTree {
        private Node root;
    
        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;
        }
    
        // 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);
                }
            }
    
        }
    
        // 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/15146962.html
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