Maximum Binary Tree II
<p>A <strong>maximum tree</strong> is a tree where every node has a value greater than any other value in its subtree.</p>

<p>You are given the <code>root</code> of a maximum binary tree and an integer <code>val</code>.</p>

<p>Just as in the <a href="https://leetcode.com/problems/maximum-binary-tree/" target="_blank">previous problem</a>, the given tree was constructed from a list <code>a</code> (<code>root = Construct(a)</code>) recursively with the following <code>Construct(a)</code> routine:</p>

<ul>
	<li>If <code>a</code> is empty, return <code>null</code>.</li>
	<li>Otherwise, let <code>a[i]</code> be the largest element of <code>a</code>. Create a <code>root</code> node with the value <code>a[i]</code>.</li>
	<li>The left child of <code>root</code> will be <code>Construct([a[0], a[1], ..., a[i - 1]])</code>.</li>
	<li>The right child of <code>root</code> will be <code>Construct([a[i + 1], a[i + 2], ..., a[a.length - 1]])</code>.</li>
	<li>Return <code>root</code>.</li>
</ul>

<p>Note that we were not given <code>a</code> directly, only a root node <code>root = Construct(a)</code>.</p>

<p>Suppose <code>b</code> is a copy of <code>a</code> with the value <code>val</code> appended to it. It is guaranteed that <code>b</code> has unique values.</p>

<p>Return <code>Construct(b)</code>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://fastly.jsdelivr.net/gh/doocs/leetcode@main/solution/0900-0999/0998.Maximum%20Binary%20Tree%20II/images/maxtree1.jpg" style="width: 376px; height: 235px;" />
<pre>
<strong>Input:</strong> root = [4,1,3,null,null,2], val = 5
<strong>Output:</strong> [5,4,null,1,3,null,null,2]
<strong>Explanation:</strong> a = [1,4,2,3], b = [1,4,2,3,5]
</pre>

<p><strong class="example">Example 2:</strong></p>
<img alt="" src="https://fastly.jsdelivr.net/gh/doocs/leetcode@main/solution/0900-0999/0998.Maximum%20Binary%20Tree%20II/images/maxtree21.jpg" style="width: 358px; height: 156px;" />
<pre>
<strong>Input:</strong> root = [5,2,4,null,1], val = 3
<strong>Output:</strong> [5,2,4,null,1,null,3]
<strong>Explanation:</strong> a = [2,1,5,4], b = [2,1,5,4,3]
</pre>

<p><strong class="example">Example 3:</strong></p>
<img alt="" src="https://fastly.jsdelivr.net/gh/doocs/leetcode@main/solution/0900-0999/0998.Maximum%20Binary%20Tree%20II/images/maxtree3.jpg" style="width: 404px; height: 180px;" />
<pre>
<strong>Input:</strong> root = [5,2,3,null,1], val = 4
<strong>Output:</strong> [5,2,4,null,1,3]
<strong>Explanation:</strong> a = [2,1,5,3], b = [2,1,5,3,4]
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li>The number of nodes in the tree is in the range <code>[1, 100]</code>.</li>
	<li><code>1 &lt;= Node.val &lt;= 100</code></li>
	<li>All the values of the tree are <strong>unique</strong>.</li>
	<li><code>1 &lt;= val &lt;= 100</code></li>
</ul>
Tree; Binary Tree
// Definition for a binary tree node.
// #[derive(Debug, PartialEq, Eq)]
// pub struct TreeNode {
//   pub val: i32,
//   pub left: Option<Rc<RefCell<TreeNode>>>,
//   pub right: Option<Rc<RefCell<TreeNode>>>,
// }
//
// impl TreeNode {
//   #[inline]
//   pub fn new(val: i32) -> Self {
//     TreeNode {
//       val,
//       left: None,
//       right: None
//     }
//   }
// }
use std::cell::RefCell;
use std::rc::Rc;
impl Solution {
    pub fn insert_into_max_tree(
        mut root: Option<Rc<RefCell<TreeNode>>>,
        val: i32,
    ) -> Option<Rc<RefCell<TreeNode>>> {
        if root.is_none() || root.as_ref().unwrap().as_ref().borrow().val < val {
            return Some(Rc::new(RefCell::new(TreeNode {
                val,
                left: root.take(),
                right: None,
            })));
        }
        {
            let mut root = root.as_ref().unwrap().as_ref().borrow_mut();
            root.right = Self::insert_into_max_tree(root.right.take(), val);
        }
        root
    }
}
