36: binary search trees and doubly-linked list

Title Description

Enter a binary search tree, the binary search tree converted into a doubly linked list sorted. Requirements can not create any new node, point to only adjust the tree node pointer.

 

method 1:

Ideas: the BST inorder traversal, the nodes stored in queue, the queue sequentially eject nodes, and follow the pop order to reconnect all the nodes.

 1 import java.util.*;
 2 class TreeNode {
 3     int val = 0;
 4     TreeNode left = null;
 5     TreeNode right = null;
 6 
 7     public TreeNode(int val) {
 8         this.val = val;
 9 
10     }
11 
12 }
13 public class Solution {
14     public TreeNode Convert(TreeNode pRootOfTree) {
15         Queue<TreeNode> queue=new LinkedList<TreeNode>();
16         inOrderToQueue(pRootOfTree,queue);
17         if (queue.isEmpty()) {
18             return pRootOfTree;
19         }
20         TreeNode head=queue.poll();
21         TreeNode pre=head;
22         pre.left=null;
23         TreeNode cur=null;
24         while (!queue.isEmpty()) {
25             cur=queue.poll();
26             pre.right=cur;
27             cur.left=pre;
28             pre=cur;
29         }
30         pre.right=null;
31         return head;
32     }
33     public void inOrderToQueue(TreeNode node,Queue<TreeNode> queue) {
34         if (node==null) {
35             return;
36         }
37         inOrderToQueue(node.left,queue);
38         queue.offer(node);
39         inOrderToQueue(node.right,queue);
40     }
41 }