solve

It's MLK day, here's some more binary tree questions

preorder and inorder: problem

from typing import Optional
# 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]:

        if not preorder:
            return None

        val = preorder[0]

        split_index = -1
        for i, v in enumerate(inorder):
            if v == val:
                split_index = i

        left_preorder = preorder[1:1+split_index]
        right_preorder = preorder[1+split_index:]
        left_inorder = inorder[0:split_index]
        right_inorder = inorder[split_index+1:]

        return TreeNode(
            val = val,
            left = self.buildTree(left_preorder, left_inorder),
            right = self.buildTree(right_preorder, right_inorder)
        )

inorder and postorder: problem

from typing import Optional
# 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]:
        if not inorder:
            return None
        val = postorder[-1]
        split_index = -1
        for i, v in enumerate(inorder):
            if v == val:
                split_index = i
        left_inorder = inorder[0:split_index]
        right_inorder = inorder[split_index+1:]
        left_postorder = postorder[0:split_index]
        right_postorder = postorder[split_index:len(postorder)-1]

        return TreeNode(
            val=val,
            left=self.buildTree(left_inorder, left_postorder),
            right=self.buildTree(right_inorder, right_postorder)
        )