Given a binary tree
struct TreeLinkNode { TreeLinkNode *left; TreeLinkNode *right; TreeLinkNode *next; }
Populate each next pointer to point to its next right node. If there is no next right node, the next pointer should be set to NULL
.
Initially, all next pointers are set to NULL
.
Note:
- You may only use constant extra space.
- You may assume that it is a perfect binary tree (ie, all leaves are at the same level, and every parent has two children).
For example,
Given the following perfect binary tree,
1 / \ 2 3 / \ / \ 4 5 6 7
After calling your function, the tree should look like:
1 -> NULL / \ 2 -> 3 -> NULL / \ / \ 4->5->6->7 -> NULL
代码如下:
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 a=1;12 int b=a;13 List<TreeLinkNode> list=LevelTraverse(root);14 15 try{16 int i=0;17 while(i<list.size())18 {19 TreeLinkNode node=list.get(i);20 i++;21 b=b-1;22 while(b>0)23 {24 node.next=list.get(i);25 i++;26 node=node.next;27 b--;28 }29 node.next=null;30 b=a*2;31 a=b;32 }33 }catch(NullPointerException e){}34 35 }36 public ArrayList<TreeLinkNode> LevelTraverse(TreeLinkNode root)//树的水平遍历37 {38 ArrayList<TreeLinkNode> list=new ArrayList<TreeLinkNode>();39 Queue<TreeLinkNode> queue = new LinkedList<TreeLinkNode>();40 queue.add(root);41 try{42 while(queue.size()>0)43 {44 TreeLinkNode a=(TreeLinkNode)queue.peek();45 queue.remove();46 list.add(a);47 if(a.left!=null)48 queue.add(a.left);49 if(a.right!=null)50 queue.add(a.right);51 }52 }catch(NullPointerException e){}53 54 return list;55 }56 }
原标题:116. Populating Next Right Pointers in Each Node
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