[Solved] Consider the following buggy deserialization code snippet for BFS-based tree reconstruction.... Which line contains the subtle bug that causes incorrect tree structure when deserializing? | Tree: Depth-First Search

Tree: Depth-First Search - Serialize and Deserialize Binary Tree

Consider the following buggy deserialization code snippet for BFS-based tree reconstruction. Which line contains the subtle bug that causes incorrect tree structure when deserializing?

def deserialize(data):
    if not data:
        return None
    vals = data.split(',')
    root = TreeNode(int(vals[0]))
    queue = deque([root])
    i = 1
    while queue:
        node = queue.popleft()
        if vals[i] != 'X':
            node.left = TreeNode(int(vals[i]))
            queue.append(node.left)
        i += 1
        if vals[i] != 'X':
            node.right = TreeNode(int(vals[i]))
            queue.append(node.right)
        i += 1
    return root

ALine: if vals[i] != 'X': (left child check)

BLine: i += 1 (after left child assignment)

CLine: if vals[i] != 'X': (right child check)

DLine: while queue: (loop condition)

Step-by-Step Solution

Step 1: Identify potential infinite loop
The loop condition 'while queue:' does not check if 'i' has exceeded vals length, risking index out of range or infinite loop.
Step 2: Understand impact on deserialization
Without checking 'i < len(vals)', the loop may continue after all nodes processed, causing errors or incorrect tree structure.
Final Answer:
Option D -> Option D
Quick Check:
Loop condition must ensure 'i' stays within bounds to avoid deserialization bugs [OK]

Quick Trick: Loop must check index bounds to avoid infinite loops [OK]

Common Mistakes:

MISTAKES

Not checking index bounds in deserialization loops
Mixing up left and right child assignments
Forgetting to append children to queue

Trap Explanation:

PITFALL

Candidates often overlook loop termination conditions related to input length, causing subtle bugs.

Interviewer Note:

CONTEXT

Tests attention to boundary conditions and loop invariants in deserialization code.

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More Tree: Depth-First Search Quizzes

Consider the following buggy deserialization code snippet for BFS-based tree reconstruction. Which line contains the subtle bug that causes incorrect tree structure when deserializing?

Step 1: Identify potential infinite loop

Step 2: Understand impact on deserialization

Final Answer:

Quick Check:

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