Which approach guarantees reconstructing the original tree efficiently without redundant subtree searches?
easy🔍 Pattern Recognition Q11 of Q15
Tree: Depth-First Search - Construct Tree from Preorder and Inorder
You are given two arrays representing the preorder and inorder traversal sequences of a binary tree. Which approach guarantees reconstructing the original tree efficiently without redundant subtree searches?
AUse breadth-first search to build the tree level by level from preorder and inorder arrays.
BUse a greedy approach that picks nodes based on preorder and attaches them arbitrarily to the left or right.
CUse dynamic programming to store subtree results and combine them for the full tree.
DUse recursion with a hash map to quickly find root indices in inorder traversal, avoiding repeated searches.
Step-by-Step Solution
Step 1: Understand the problem constraints
Reconstructing a binary tree from preorder and inorder requires knowing root positions quickly to split subtrees.
Step 2: Identify the optimal approach
Using a hash map for inorder indices allows O(1) root lookups, avoiding repeated O(n) searches in recursion.
