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Consider the optimized recursive solution for building a tree from inorder and postorder traversals. Given inorder = [1] and postorder = [1], what is the structure of the constructed tree?

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Tree: Depth-First Search - Construct Tree from Inorder and Postorder

Consider the optimized recursive solution for building a tree from inorder and postorder traversals. Given inorder = [1] and postorder = [1], what is the structure of the constructed tree?

AA tree with root 1 and both left and right children as None

BA tree with root 1 and a left child 1

CA tree with root 1 and a right child 1

DAn empty tree (None)

Step-by-Step Solution

Solution:

Step 1: Base case with single element arrays
in_left == in_right == 0, post_left == post_right == 0, root_val = 1.
Step 2: Recursive calls for left and right subtrees
Left subtree: in_left=0, in_right=-1 -> None; Right subtree: in_left=1, in_right=0 -> None.
Final Answer:
Option A -> Option A
Quick Check:
Single node tree with no children [OK]

Quick Trick: Single element arrays produce single node tree [OK]

Common Mistakes:

MISTAKES

Assuming extra children exist
Returning None incorrectly

Trap Explanation:

PITFALL

Candidates sometimes add children incorrectly or return None for single node.

Interviewer Note:

CONTEXT

Tests handling of minimal edge case input in recursion.

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