出鞘之剑指offer-第36题 (二叉搜索树与双向链表)

题目：

 输入一棵二叉搜索树，将该二叉搜索树转换成一个排序的双向链表。要求不能创建任何新的节点，只能调整树中结点指针的指向。

分析一：

 

代码一：

package offer.xzs.thirty2thirtynine.thirtysix;

import java.util.Arrays;

public class Demo01 {
    public static BinaryTree head = null;
    public static BinaryTree pre = null;

    public static void main(String[] args) {
        int[] pre = { 10, 6, 4, 8, 14, 12, 16 };
        int[] mid = { 4, 6, 8, 10, 12, 14, 16 };
        BinaryTree root = build(pre, mid);
        BinaryTree doubleLinkList = getDoubleLinkList(root);
        System.out.println(doubleLinkList);
    }

    public static BinaryTree getDoubleLinkList(BinaryTree tree) {
        doThis(tree);
        return head;
    }

    private static void doThis(BinaryTree tree) {
        if (tree == null) {
            return;
        }
        doThis(tree.getLeft());
        if (pre != null) {
            pre.setRight(tree);
            tree.setLeft(pre);
        }
        pre = tree;
        if (head == null) {
            head = tree;
        }
        doThis(tree.getRight());
    }

    //建二叉树
    public static BinaryTree build(int[] preList, int[] midList) {
        if (preList == null || preList.length == 0 || midList == null || midList.length == 0 || preList.length != midList.length) {
            return null;
        }
        BinaryTree root = new BinaryTree(preList[0]);
        for (int i = 0; i < preList.length; i++) {
            if (preList[0] == midList[i]) {
                root.setLeft(build(Arrays.copyOfRange(preList, 1, i + 1), Arrays.copyOfRange(midList, 0, i)));
                root.setRight(build(Arrays.copyOfRange(preList, i + 1, preList.length), Arrays.copyOfRange(midList, i + 1, midList.length)));
            }
        }
        return root;
    }
    //先序遍历
    public static void preShow(BinaryTree root) {
        if (root == null) {
            return;
        }
        System.out.printf("%d\t", root.getValue());
        if (root.getLeft() != null) {
            preShow(root.getLeft());
        }
        if (root.getRight() != null) {
            preShow(root.getRight());
        }

    }
}