Bit Manipulation - Gray Code
Consider the following buggy Python code intended to generate Gray code sequence. Which line contains the subtle bug that breaks the Gray code property?
Consider the following buggy Python code intended to generate Gray code sequence. Which line contains the subtle bug that breaks the Gray code property?
medium🐞 Bug Identification Q14 of Q15
Step-by-Step Solution
Solution:
Step 1: Identify the bitwise operation used
The code uses i ^ (i << 1) instead of the correct i ^ (i >> 1).Step 2: Understand impact on Gray code property
Left shifting i doubles the value, causing incorrect bit patterns and breaking the one-bit difference property between consecutive numbers.Final Answer:
Option A -> Option AQuick Check:
Correct Gray code uses right shift, not left shift [OK]
Quick Trick: XOR with right shift generates Gray code; left shift breaks it [OK]
Common Mistakes:
MISTAKES- Confusing left and right bit shifts in XOR formula
- Ignoring base case n=0 which is trivial but not critical here
- Misunderstanding range boundaries or print vs return
Trap Explanation:
PITFALL- The left shift looks similar but changes the sequence drastically; other lines look plausible but are correct.
Interviewer Note:
CONTEXT- Checks if candidate understands the exact bitwise formula and its correctness conditions.
Master "Gray Code" in Bit Manipulation
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