Which approach guarantees that the tree structure, including null children, is preserved and can be reconstructed efficiently?
easy🔍 Pattern Recognition Q11 of Q15
Tree: Depth-First Search - Serialize and Deserialize Binary Tree
You need to convert a binary tree into a string and then reconstruct the exact same tree from that string. Which approach guarantees that the tree structure, including null children, is preserved and can be reconstructed efficiently?
AUse level order traversal (BFS) including null markers for missing children, then deserialize by reading nodes level by level.
BUse a greedy traversal that records only node values without null markers, then reconstruct by inserting nodes in order.
CUse dynamic programming to store subtree encodings and reconstruct from stored subtrees.
DUse inorder traversal without null markers and reconstruct by assuming a balanced tree.
Step-by-Step Solution
Step 1: Understand the need for null markers
Without null markers, the tree structure cannot be uniquely reconstructed because missing children are ambiguous.
Step 2: Recognize BFS with null markers preserves structure
Level order traversal with null markers records nodes level by level, capturing the exact shape of the tree, enabling correct deserialization.
Final Answer:
Option A -> Option A
Quick Check:
Level order with null markers uniquely encodes tree structure [OK]
Quick Trick:Null markers are essential to preserve tree shape [OK]
Common Mistakes:
MISTAKES
Ignoring null markers leads to ambiguous deserialization
Assuming inorder traversal alone can reconstruct arbitrary trees
Using greedy or DP approaches that don't preserve structure
Trap Explanation:
PITFALL
Many candidates think preorder or inorder without nulls suffices, but that loses structure information.
Interviewer Note:
CONTEXT
Tests if candidate understands why null markers and BFS are needed for correct serialization.
Master "Serialize and Deserialize Binary Tree" in Tree: Depth-First Search
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