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 +
                '}';
    }
}