116. Populating Next Right Pointers in Each Node

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

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;    }}

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