<p>Given two integer arrays <code>inorder</code> and <code>postorder</code> where <code>inorder</code> is the inorder traversal of a binary tree and <code>postorder</code> is the postorder traversal of the same tree, construct and return <em>the binary tree</em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2021/02/19/tree.jpg" style="width: 277px; height: 302px;" />
<pre>
<strong>Input:</strong> inorder = [9,3,15,20,7], postorder = [9,15,7,20,3]
<strong>Output:</strong> [3,9,20,null,null,15,7]
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> inorder = [-1], postorder = [-1]
<strong>Output:</strong> [-1]
</pre>

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

<ul>
	<li><code>1 &lt;= inorder.length &lt;= 3000</code></li>
	<li><code>postorder.length == inorder.length</code></li>
	<li><code>-3000 &lt;= inorder[i], postorder[i] &lt;= 3000</code></li>
	<li><code>inorder</code> and <code>postorder</code> consist of <strong>unique</strong> values.</li>
	<li>Each value of <code>postorder</code> also appears in <code>inorder</code>.</li>
	<li><code>inorder</code> is <strong>guaranteed</strong> to be the inorder traversal of the tree.</li>
	<li><code>postorder</code> is <strong>guaranteed</strong> to be the postorder traversal of the tree.</li>
</ul>

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def buildTree(self, inorder: List[int], postorder: List[int]) -> Optional[TreeNode]:
        n = len(postorder)
        reverse = {}
        for i, x in enumerate(inorder):
            reverse[x] = i
        stack = [(postorder.pop(), 0, n - 1)]
        visited = [0]
        res = []
        while stack:
            node, start, end = stack[-1]
            if visited[-1] == 0:
                visited[-1] = 1
                if reverse[node] + 1 <= end:
                    stack.append((postorder.pop(), reverse[node] + 1, end))
                    visited.append(False)
            elif visited[-1] == 1:
                visited[-1] = 2
                if start <= reverse[node] - 1:
                    stack.append((postorder.pop(), start, reverse[node] - 1))
                    visited.append(False)
            else:
                stack.pop()
                visited.pop()
                cur = TreeNode(node)
                if start <= reverse[node] - 1:
                    cur.left = res.pop()
                if reverse[node] + 1 <= end:
                    cur.right = res.pop()
                res.append(cur)
        return res[0]
18000