Return the root node of a binary search tree that matches the given preorder traversal.
(Recall that a binary search tree is a binary tree where for every node, any descendant of node.left has a value < node.val, and any descendant of node.right has a value > node.val.  Also recall that a preorder traversal displays the value of the node first, then traverses node.left, then traverses node.right.)
It's guaranteed that for the given test cases there is always possible to find a binary search tree with the given requirements.
Example 1:
Input: [8,5,1,7,10,12]
Output: [8,5,10,1,7,null,12]
Constraints:
1 <= preorder.length <= 100
1 <= preorder[i] <= 10^8
The values of preorder are distinct.
# 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 bstFromPreorder(self, preorder: List[int]) -> TreeNode:
        # time O(n); space O(n)
        vals = deque(preorder)
        
        def build(min_val, max_val):
            if vals and min_val < vals[0] < max_val:
                val = vals.popleft()
                node = TreeNode(val)
                node.left = build(min_val, val)
                node.right = build(val, max_val)
                
                return node
        
        return build(float('-inf'), float('inf'))
# 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 bstFromPreorder(self, preorder: List[int]) -> TreeNode:
        # time O(n); space O(n)
        vals = deque(preorder)
        
        def build(min_val, max_val):
            if vals and min_val < vals[0] < max_val:
                val = vals.popleft()
                node = TreeNode(val)
                node.left = build(min_val, val)
                node.right = build(val, max_val)
                
                return node
        
        return build(float('-inf'), float('inf'))