# Populating Next Right Pointers in Each Node II

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.
* Recursive approach is fine, implicit stack space does not count as extra space for this problem.

## **Example**

Given the following binary tree,

```
     1
   /  \
  2    3
 / \    \
4   5    7
```

After calling your function, the tree should look like:

```
     1 -> NULL
   /  \
  2 -> 3 -> NULL
 / \    \
4-> 5 -> 7 -> NULL
```

## Note

和之前不一样的是，这里不一定是perfect树了，所以会跨左右孩子，右连右这种情况

需要另外记一个head（这一层的第一个）和pre（前一个节点），根据这些进行连接

## Code

```java
public void connect(TreeLinkNode root) {
    TreeLinkNode cur  = root;
    TreeLinkNode pre  = null;
    TreeLinkNode head = null;
    while (cur != null) {
        while (cur != null) {
            if (cur.left != null) {
                if (pre != null) {
                    pre.next = cur.left;
                } else 
                    head = cur.left; 
                pre = cur.left;
            }
            if (cur.right != null) {
                if (pre != null) {
                    pre.next = cur.right;
                } else 
                    head = cur.right; 
                pre = cur.right;   
            }
            cur = cur.next;
        }
        cur  = head;
        pre  = null;
        head = null;
    }
}
```


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://luj.gitbook.io/code/tree/9-structure/populating-next-right-pointers-in-each-node-ii.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.