<p>Given two integer arrays <code>preorder</code> and <code>inorder</code> where <code>preorder</code> is the preorder traversal of a binary tree and <code>inorder</code> is the inorder 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> preorder = [3,9,20,15,7], inorder = [9,3,15,20,7]
<strong>Output:</strong> [3,9,20,null,null,15,7]
</pre>

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

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

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

<ul>
	<li><code>1 &lt;= preorder.length &lt;= 3000</code></li>
	<li><code>inorder.length == preorder.length</code></li>
	<li><code>-3000 &lt;= preorder[i], inorder[i] &lt;= 3000</code></li>
	<li><code>preorder</code> and <code>inorder</code> consist of <strong>unique</strong> values.</li>
	<li>Each value of <code>inorder</code> also appears in <code>preorder</code>.</li>
	<li><code>preorder</code> is <strong>guaranteed</strong> to be the preorder traversal of the tree.</li>
	<li><code>inorder</code> is <strong>guaranteed</strong> to be the inorder 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, preorder: List[int], inorder: List[int]) -> Optional[TreeNode]:
        debug = False
        i, j = 0, 0
        root = TreeNode(preorder[0])
        stack = [root]
    
        while i < len(preorder):
            
            if debug: print(f'P0 i: {i} j:{j} stack: {stack}')
            while stack[-1].val != inorder[j]:
                i += 1
                stack[-1].left = TreeNode(preorder[i])
                stack.append(stack[-1].left)
            
            if i < len(preorder)-1: 
                i+= 1
            else:
                break


            if debug: print(f'P1 i: {i} j:{j} stack: {stack}')

            while stack and inorder[j] == stack[-1].val:
                node = stack.pop()
                j+=1
            if debug: print(f'P2 i: {i} j:{j} stack: {stack}')
            node.right = TreeNode(preorder[i])
            stack.append(node.right)
            if debug: print(f'P3 i: {i} j:{j} stack: {stack}\n')                       
            

        return root
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