<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]:
        nodesToIndex = {}
        n = len(inorder)
        for i in range(n):
            nodesToIndex[inorder[i]] = i

        def build(inStart, inEnd, postStart, postEnd):
            if inStart == inEnd:
                return TreeNode(postorder[postEnd])
            if inStart > inEnd or postStart > postEnd:
                return None

            print(postEnd)

            root = TreeNode(postorder[postEnd])
            rootIndex = nodesToIndex[root.val]
            inEndL = rootIndex - 1
            inStartL = inStart
            inStartR = rootIndex + 1
            inEndR = inEnd
            rightSubtreeSize = inEndR - inStartR + 1
            postEndR = postEnd - 1
            postStartR = postEnd - rightSubtreeSize
            postEndL = postStartR - 1
            postStartL = postStart

            print(root.val, inStartL, inEndL, postStartL, postEndL)
            print(inStartR, inEndR, postStartR, postEndR)
            root.left = build(inStartL, inEndL, postStartL, postEndL)

            root.right = build(inStartR, inEndR, postStartR, postEndR)

            return root
        return build(0, n - 1, 0, n - 1)
            

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