Tree Construction
Detailed guide and Python implementation for the 'Tree Construction' problem.
Problem Statement
Write a function build_tree(preorder, inorder) that reconstructs a binary tree from its preorder and inorder traversal lists and returns the level-order traversal of the reconstructed tree (represented as a list, with None for empty nodes).
- •1 <= len(preorder) <= 1000
- •inorder.length == preorder.length
Examples
preorder = [3, 9, 20, 15, 7], inorder = [9, 3, 15, 20, 7]
[3, 9, 20, None, None, 15, 7]
Preorder allows identifying the root 3. Inorder splits left subtree [9] and right subtree [15, 20, 7]. Reconstructed tree has level order [3, 9, 20, None, None, 15, 7].
Need a Hint?
Edge Cases to Watch
- Empty input structures
- Single element inputs
- Large numerical bounds
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