Construct Binary Tree from Preorder and Inorder Traversal

Given the preorder and inorder serialization of a binary tree, construct a tree data structure. Tags: Recursion, Search, Trees

Try It!

Discussion

Video

Solution

# 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]) -> TreeNode:
        if not inorder:
            return None
        
        root = preorder.pop(0)
        idx = inorder.index(root)
        node = TreeNode(root)
        node.left = self.buildTree(preorder, inorder[:idx])
        node.right = self.buildTree(preorder, inorder[idx + 1:])
        return node