Tree: Depth-First Search - Flatten Binary Tree to Linked List
Given the final flattened linked list sequence [1, 2, 3, 4, 5, 6] obtained by the optimal flatten algorithm, which of the following was the original binary tree structure?
Given the final flattened linked list sequence [1, 2, 3, 4, 5, 6] obtained by the optimal flatten algorithm, which of the following was the original binary tree structure?
hard🔄 Reverse Engineer Q9 of Q15
Step-by-Step Solution
Solution:
Step 1: Analyze preorder sequence
Sequence 1,2,3,4,5,6 suggests root 1, left subtree nodes 2,3,4, right subtree nodes 5,6.Step 2: Match to tree structure
Balanced tree with root 1, left subtree (2,3,4), right subtree (5,6) matches this preorder.Final Answer:
Option D -> Option DQuick Check:
Preorder sequence matches balanced tree structure [OK]
Quick Trick: Preorder sequence reveals original tree shape [OK]
Common Mistakes:
MISTAKES- Assuming skewed tree from linear list
- Ignoring subtree grouping in preorder
Trap Explanation:
PITFALL- Candidates often mistake linear list for skewed tree ignoring subtree structure.
Interviewer Note:
CONTEXT- Tests ability to reason backwards from output to input tree.
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