二叉搜索树与双向链表-剑指Offer

Posted 2020-08-01 RosenDing

二叉搜索树与双向链表

题目描述

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结点，只能调整树中结点指针的指向。

思路

1. 按中序遍历二叉搜索树可从小到大遍历元素
2. 边遍历元素边创建双向链表
3. 最后得到的双向链表的指针指向最后一个节点，所以需要再往回遍历一遍让指针指到头结点

代码

/**
public class TreeNode {
    int val = 0;
    TreeNode left = null;
    TreeNode right = null;

    public TreeNode(int val) {
        this.val = val;

    }

}
*/
public class Solution {
    public TreeNode Convert(TreeNode pRootOfTree) {
        TreeNode listNode = null;
        listNode = myConvert(pRootOfTree, listNode);
        TreeNode listHead = listNode;
        while (listHead != null && listHead.left != null) {
        	listHead = listHead.left;
        }
        return listHead;
    }
public TreeNode myConvert(TreeNode node, TreeNode listNode) {
	if (node == null) {
		return null;
	}
	TreeNode current = node;
	if (current.left != null) {
		listNode = myConvert(current.left, listNode);
	}
	current.left = listNode;
	if (listNode != null) {
		listNode.right = current;
	}
	listNode = current;
	if (current.right != null) {
		listNode = myConvert(current.right, listNode);
	}
	return listNode;
}
}