Tree: Depth-First Search - Construct Tree from Preorder and Inorder
Given the following partial inorder_index_map: {3:1, 9:0, 20:3, 15:2, 7:4} and preorder traversal [3,9,20,15,7], which node is the root of the right subtree of the root node 3?
Given the following partial inorder_index_map: {3:1, 9:0, 20:3, 15:2, 7:4} and preorder traversal [3,9,20,15,7], which node is the root of the right subtree of the root node 3?
hard🔄 Reverse Engineer Q9 of Q15
Step-by-Step Solution
Solution:
Step 1: Identify root node
Root is preorder[0] = 3.Step 2: Find right subtree root
Right subtree root is next preorder node after left subtree, which is 20.Final Answer:
Option C -> Option CQuick Check:
Right subtree root follows left subtree in preorder [OK]
Quick Trick: Right subtree root is preorder after left subtree nodes [OK]
Common Mistakes:
MISTAKES- Confusing left and right subtree roots
Trap Explanation:
PITFALL- Candidates pick left child or later nodes incorrectly.
Interviewer Note:
CONTEXT- Tests ability to reason backwards from traversal indices
Master "Construct Tree from Preorder and Inorder" in Tree: Depth-First Search
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