Tree: Depth-First Search - Serialize and Deserialize Binary Tree
Given the following BFS-based serialization code snippet, what is the serialized string output for the binary tree with root 1, left child 2, and right child null?
Given the following BFS-based serialization code snippet, what is the serialized string output for the binary tree with root 1, left child 2, and right child null?
easy🧾 Code Trace Q3 of Q15
Step-by-Step Solution
Solution:
Step 1: Trace BFS serialization
Start with root 1: append '1', enqueue left(2), right(None). Next dequeue 2: append '2', enqueue left(None), right(None). Next dequeue None: append 'X'. Next dequeue None: append 'X'. Next dequeue None: append 'X'.Step 2: Remove trailing 'X's
Trailing 'X's are removed until last element is not 'X'. The last three 'X's are removed, leaving "1,2".Final Answer:
Option A -> Option AQuick Check:
Trailing null markers are trimmed in BFS serialization [OK]
Quick Trick: Trailing null markers are trimmed in BFS serialization [OK]
Common Mistakes:
MISTAKES- Including all null markers without trimming
- Miscounting nodes in BFS order
Trap Explanation:
PITFALL- Candidates often forget the trimming step and include trailing 'X's in output.
Interviewer Note:
CONTEXT- Tests candidate's ability to mentally execute BFS serialization with trimming.
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