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
My code:
/** * Definition for binary tree with next pointer. * public class TreeLinkNode { * int val; * TreeLinkNode left, right, next; * TreeLinkNode(int x) { val = x; } * } */public class Solution { public void connect(TreeLinkNode root) { Queue<TreeLinkNode> queue = new LinkedList<>(); if(root==null) return; queue.offer(root); while(!queue.isEmpty()){ int qSize = queue.size(); for (int i=0;i<qSize;i++){ TreeLinkNode cur = queue.poll(); if(i!=qSize-1) cur.next = queue.peek(); else cur.next = null; if (cur.left!=null) queue.offer(cur.left); if (cur.right!=null) queue.offer(cur.right); } } } }
总结:你是最棒的,不急不躁,慢慢来。加油啦。一切都会好的。
O(n)space,O(n)time
改进:
public class Solution { public void connect(TreeLinkNode root) { TreeLinkNode level_start=root; while(level_start!=null){ TreeLinkNode cur=level_start; while(cur!=null){ if(cur.left!=null) cur.left.next=cur.right; if(cur.right!=null && cur.next!=null) cur.right.next=cur.next.left; cur=cur.next; } level_start=level_start.left; } }}
O(1)space, O(n)time
0 0
- Populating Next Right Pointers in Each Node
- Populating Next Right Pointers in Each Node
- Populating Next Right Pointers in Each Node
- Populating Next Right Pointers in Each Node
- Populating Next Right Pointers in Each Node
- Populating Next Right Pointers in Each Node
- Populating Next Right Pointers in Each Node
- Populating Next Right Pointers in Each Node
- Populating Next Right Pointers in Each Node
- Populating Next Right Pointers in Each Node
- Populating Next Right Pointers in Each Node
- Populating Next Right Pointers in Each Node
- Populating Next Right Pointers in Each Node
- Populating Next Right Pointers in Each Node
- Populating Next Right Pointers in Each Node
- Populating Next Right Pointers in Each Node
- Populating Next Right Pointers in Each Node
- Populating Next Right Pointers in Each Node
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