Bit Manipulation - UTF-8 Validation
Given the following code snippet for UTF-8 validation, what is the return value when input is [197, 130, 1]?
Given the following code snippet for UTF-8 validation, what is the return value when input is [197, 130, 1]?
easy🧾 Code Trace Q3 of Q15
Step-by-Step Solution
Solution:
Step 1: Trace first byte 197 (0b11000101)
Leading bits 110 -> remaining = 1 (expect 1 continuation byte)Step 2: Check second byte 130 (0b10000010)
Starts with 10 -> valid continuation byte, remaining decremented to 0Step 3: Check third byte 1 (0b00000001)
Starts with 0 -> single byte character, remaining stays 0Step 4: End of data, remaining == 0 -> valid UTF-8
Final Answer:
Option C -> Option CQuick Check:
All bytes valid and remaining zero at end [OK]
Quick Trick: Check continuation byte count matches [OK]
Common Mistakes:
MISTAKES- Forgetting to decrement remaining
- Misreading leading bits
Trap Explanation:
PITFALL- Candidates often miss decrementing remaining or misinterpret leading bits causing false negatives.
Interviewer Note:
CONTEXT- Tests ability to mentally execute bitmasking logic on typical input.
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