leetcode------Populating Next Right Pointers in Each Node II

标题： Populating Next Right Pointers in Each Node II
通过率： 31.7%
难度： 难

Follow up for problem "Populating Next Right Pointers in Each Node".

What if the given tree could be any binary tree? Would your previous solution still work?

Note:

  • You may only use constant extra space.

 

For example,
Given the following binary tree,

         1
       /  \
      2    3
     / \    \
    4   5    7

 

After calling your function, the tree should look like:

         1 -> NULL
       /  \
      2 -> 3 -> NULL
     / \    \
    4-> 5 -> 7 -> NULL


本题跟第一个版本一样，就是按层次遍历就行了。具体看代码
 1 /**
 2  * Definition for binary tree with next pointer.
 3  * public class TreeLinkNode {
 4  *     int val;
 5  *     TreeLinkNode left, right, next;
 6  *     TreeLinkNode(int x) { val = x; }
 7  * }
 8  */
 9 public class Solution {
10     public void connect(TreeLinkNode root) {
11         int count=1,tmp=0;
12         LinkedList<TreeLinkNode> queue=new LinkedList<TreeLinkNode>();
13         TreeLinkNode start=null,sec=null,pre=null;
14         if(root!=null){
15          queue.addLast(root);
16         }
17         while(!queue.isEmpty()){
18             pre=queue.pollFirst();
19                 if(count==1)pre.next=null;
20                 if(pre.left!=null){
21                     queue.addLast(pre.left);
22                     tmp++;
23                 }
24                 if(pre.right!=null){
25                     queue.addLast(pre.right);
26                     tmp++;
27                 }
28 
29             for(int i=1;i<count;i++){
30                 start=queue.pollFirst();
31                 pre.next=start;
32                 pre=start;
33                 if(start.left!=null){
34                     queue.addLast(start.left);
35                     tmp++;
36                 }
37                 if(start.right!=null){
38                     queue.addLast(start.right);
39                     tmp++;
40                 }
41             }
42             count=tmp;
43             tmp=0;
44             if(start!=null)
45             start.next=null;
46         }
47         
48     }
49 }

 

posted @ 2015-03-13 12:20  pku_smile  阅读(160)  评论(0)  编辑  收藏  举报