輸入一棵二元查詢樹，將該二元查詢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，只調整指標的指向。 轉換成雙向連結串列 1=2=3=4=5=6=7=8=9=10=11=12=13=14=15。

程式碼如下

public class BinaryTree2LinkedTree {

    private static TreeNode head,tail;

    static class TreeNode{
        private int v;
        private TreeNode left;
        private TreeNode right;

        public
 
 TreeNode(int v, TreeNode left, TreeNode right) {
            this.v = v;
            this.left = left;
            this.right = right;
        }

        public int getV() {
            return v;
        }

        public void setV(int v) {
            this.v = v;
        }

        public TreeNode getLeft
 
() {
            return left;
        }

        public void setLeft(TreeNode left) {
            this.left = left;
        }

        public TreeNode getRight() {
            return right;
        }

        public void setRight(TreeNode right) {
            this.right = right;
        }
    }

    public
 
 static void traversal(TreeNode node){
        if(node ==null) return;
        if(node.getLeft()!=null) traversal(node.getLeft());
        changeNode(node);
        if(node.getRight() != null) traversal(node.getRight());
    }

    private static void changeNode(TreeNode node) {
        //初始時，雙向連結串列中無節點，head及tail均為null
        if (head == null) {
            head = node;
            tail = node;
        } else {
            //將新node的左指標指向當前tail,再將當前tail的右指標指向新node，最後將tail後移
            node.setLeft(tail);
            tail.setRight(node);
            tail = node;
        }
    }

    public static void main(String[] args) {
        TreeNode node1 = new TreeNode(1,null,null);
        TreeNode node3 = new TreeNode(3,null,null);
        TreeNode node2 = new TreeNode(2,node1,node3);

        TreeNode node5 = new TreeNode(5,null,null);
        TreeNode node7 = new TreeNode(7,null,null);
        TreeNode node6 = new TreeNode(6,node5,node7);
        TreeNode node4 = new TreeNode(4,node2,node6);

        TreeNode node9 = new TreeNode(9,null,null);
        TreeNode node11 = new TreeNode(11,null,null);
        TreeNode node10 = new TreeNode(10,node9,node11);

        TreeNode node13 = new TreeNode(13,null,null);
        TreeNode node15 = new TreeNode(15,null,null);
        TreeNode node14 = new TreeNode(14,node13,node15);
        TreeNode node12 = new TreeNode(12,node10,node14);

        TreeNode node8 = new TreeNode(8,node4,node12);

        traversal(node8);
        while (head != null) {
            System.out.print(head.getV() + "   ");
            head = head.getRight();
        }
    }
}