/**
 * 題目：二叉搜尋樹與雙向連結串列
 * 描述：輸入一棵二叉搜尋樹，將該二叉搜尋樹轉換成一個排序的雙向連結串列。要求不能建立任何新的結點，只能調整樹中結點指標的指向
 * 方案：在中序遍歷中新增前驅結點
 * */

public class Six {

    /**
     * 前序遍歷
     * */
    public static void two(BinaryTreeNode node) {
        if (node == null) {
            return;
        }
        System.out.println(node.var);
        one(node.left);
        one(node.right);
    }
    
 
/**
     * 中序遍歷
     * */
    @SuppressWarnings("unused")
    public static void one(BinaryTreeNode node) {
        BinaryTreeNode head = null;
        BinaryTreeNode realhead = null;
        if (node == null) {
            return;
        }
        one(node.left);
        if(head == null) {
            head 
 
= node;
            realhead = node;
        }else {
            head.right = node;
            node.left = head;
            head = node;
        }
        one(node.right);
    
    }
    /**
     * 後序遍歷
     * */
    public static void three(BinaryTreeNode node) {
        if (node == null) {
            
 
return;
        }
        one(node.left);
        one(node.right);
        System.out.println(node.var);
    }

    
    public static void main(String[] args) {
        BinaryTreeNode nodeRoot = new BinaryTreeNode();
        nodeRoot.var = 10;
        BinaryTreeNode nodeOne = new BinaryTreeNode();
        nodeOne.var = 6;
        BinaryTreeNode nodeTwo = new BinaryTreeNode();
        nodeTwo.var = 4;
        BinaryTreeNode nodeThree = new BinaryTreeNode();
        nodeThree.var = 8;
        BinaryTreeNode nodefour = new BinaryTreeNode();
        nodefour.var = 14;
        BinaryTreeNode nodeFive = new BinaryTreeNode();
        nodeFive.var = 12;
        BinaryTreeNode nodeSix = new BinaryTreeNode();
        nodeSix.var = 16;
        nodeRoot.left = nodeOne;
        nodeRoot.right = nodefour;
        nodeOne.left = nodeTwo;
        nodeOne.right = nodeThree;
        nodefour.left = nodeFive;
        nodefour.right = nodeSix;
        
        one(nodeRoot);
    }
    static class BinaryTreeNode{    
        int var;
        BinaryTreeNode left;
        BinaryTreeNode right;
    }
}