116. Populating Next Right Pointers in Each Node
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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 }
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