116. Populating Next Right Pointers in Each Node-优快云博客

本文介绍了一种在完美二叉树中填充每个节点的next指针的方法，使得每个节点指向其右侧相邻节点。通过巧妙利用层级遍历技巧，在常数额外空间条件下实现了这一目标。

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,

/ \

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

这题挺好的因为有了next指针所以现在可以直接层次遍历了

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;
    }
}