刷题--二叉搜索树与双向链表

 1 /**
 2 public 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 */
14 import java.util.*;
15 
16 public class Solution {
17     public TreeNode Convert(TreeNode pRootOfTree) {
18         // 先序遍历O(N), O(N)
19         if(pRootOfTree == null)
20             return null;
21         LinkedList<TreeNode> que = new LinkedList<TreeNode>();
22         inOrderToQueue(pRootOfTree, que);
23         TreeNode head = que.poll();
24         TreeNode cur = head;
25         while(que.isEmpty() == false){
26             cur.right = que.poll();
27             cur.right.left = cur;
28             cur = cur.right;
29         }
30         return head;
31     }
32     
33     public static void inOrderToQueue(TreeNode head, LinkedList<TreeNode> queue){
34         if(head == null)
35             return ;
36         if(head.left != null)
37             inOrderToQueue(head.left, queue);
38         queue.offer(head);
39         if(head.right != null)
40             inOrderToQueue(head.right, queue);
41     }
42 }