LeetCode 114. Flatten Binary Tree to Linked List

原题链接在这里:https://leetcode.com/problems/flatten-binary-tree-to-linked-list/description/

题目:

Given a binary tree, flatten it to a linked list in-place.

For example,
Given

         1
        / \
       2   5
      / \   \
     3   4   6

The flattened tree should look like:

   1
    \
     2
      \
       3
        \
         4
          \
           5
            \
             6

题解:

类似Flatten a Multilevel Doubly Linked List.

root.left == null时, 直接跳到root.right进行下一步.

root.left!=null 时, 目标就是把roo.left 这个子树的右边一条插进root 和 root.right之间.

Time Complexity: O(n).

Space: O(1).

AC Java:

 1 /**
 2  * Definition for a binary tree node.
 3  * public class TreeNode {
 4  *     int val;
 5  *     TreeNode left;
 6  *     TreeNode right;
 7  *     TreeNode(int x) { val = x; }
 8  * }
 9  */
10 class Solution {
11     public void flatten(TreeNode root) {
12         TreeNode cur = root;
13         while(cur != null){
14             if(cur.left == null){
15                 cur = cur.right;
16                 continue;
17             }
18             
19             TreeNode left = cur.left;
20             while(left.right != null){
21                 left = left.right; 
22             }
23             
24             left.right = cur.right;
25             cur.right = cur.left;
26             cur.left = null;
27             cur = cur.right;
28         }
29     }
30 }

 

posted @ 2015-09-09 08:03  Dylan_Java_NYC  阅读(428)  评论(0编辑  收藏  举报