class TreeNode{
    public int val;
    public TreeNode left;
    public TreeNode right;
    public TreeNode(int val){
        this.val = val;
    }
}


public class BinarySearchTree {
    TreeNode root;

    //在二叉樹(shù)中 尋找指定 val 值的節(jié)點(diǎn)
    // 找到了，返回其節(jié)點(diǎn)地址；沒(méi)找到返回 null
    public TreeNode search(int key){
        TreeNode cur = this.root;
        while(cur != null){
            if(cur.val == key){
                return cur;
            }else if(cur.val < key){
                cur = cur.right;
            }else{
                cur = cur.left;
            }
        }
        return null;
    }
    // 插入操作
    public boolean insert(int key){
        if(this.root == null){
            this.root = new TreeNode(key);
            return true;
        }
        TreeNode cur = this.root;
        TreeNode parent = null;
        while(cur!=null){
            if(key > cur.val){
                parent  = cur;
                cur = cur.right;
            }else if(cur.val == key){
                return false;
            }else{
                parent  = cur;
                cur = cur.left;
            }
        }
        TreeNode node = new TreeNode(key);
        if(parent .val > key){
            parent.left = node;
        }else{
            parent.right = node;
        }
        return true;
    }
    // 刪除操作
    public void remove(int key){
        TreeNode cur = root;
        TreeNode parent = null;
        // 尋找 刪除節(jié)點(diǎn)位置。
        while(cur!=null){
            if(cur.val == key){
                removeNode(cur,parent);// 真正刪除節(jié)點(diǎn)的代碼
                break;
            }else if(cur.val < key){
                parent = cur;
                cur = cur.right;
            }else{
                parent = cur;
                cur = cur.left;
            }
        }
    }
    // 輔助刪除方法：真正刪除節(jié)點(diǎn)的代碼
    private void removeNode(TreeNode cur,TreeNode parent){
        // 情況一
        if(cur.left == null){
            if(cur == this.root){
                this.root = this.root.right;
            }else if( cur == parent.left){
                parent.left = cur.right;
            }else{
                parent.right = cur.right;
            }
            // 情況二
        }else if(cur.right == null){
            if(cur == this.root){
                this.root = root.left;
            }else if(cur == parent.left){
                parent.left = cur.left;
            }else{
                parent.right = cur.left;
            }
            // 情況三
        }else{
            // 第二種方法：在刪除節(jié)點(diǎn)的右子樹(shù)中尋找最小值，
            TreeNode parentDummy = cur;
            TreeNode curDummy = cur.right;
            while(curDummy.left != null){
                parentDummy = curDummy;
                curDummy = curDummy.left;
            }
            // 此時(shí) curDummy 指向的 cur 右子樹(shù)
            cur.val = curDummy.val;
            if(parentDummy.left != curDummy){
                parentDummy.right = curDummy.right;
            }else{
                parentDummy.left = curDummy.right;
            }

        }
    }
   // 中序遍歷
    public void inorder(TreeNode root){
        if(root == null){
            return;
        }
        inorder(root.left);
        System.out.print(root.val+" ");
        inorder(root.right);
    }

    public static void main(String[] args) {
        int[] array = {10,8,19,3,9,4,7};
        BinarySearchTree binarySearchTree = new BinarySearchTree();
        for (int i = 0; i < array.length; i++) {
            binarySearchTree.insert(array[i]);
        }
        binarySearchTree.inorder(binarySearchTree.root);
        System.out.println();// 換行
        System.out.print("插入重復(fù)的數(shù)據(jù) 9：" + binarySearchTree.insert(9));
        System.out.println();// 換行
        System.out.print("插入不重復(fù)的數(shù)據(jù) 1：" + binarySearchTree.insert(1));
        System.out.println();// 換行
        binarySearchTree.inorder(binarySearchTree.root);
        System.out.println();// 換行
        binarySearchTree.remove(19);
        System.out.print("刪除元素 19 ：");
        binarySearchTree.inorder(binarySearchTree.root);
        System.out.println();// 換行
        System.out.print("查找不存在的數(shù)據(jù)50 ：");
        System.out.println(binarySearchTree.search(50));
        System.out.print("查找存在的數(shù)據(jù) 7：");
        System.out.println(binarySearchTree.search(7));
    }
}