Which approach best guarantees an efficient and correct validation?
easy🔍 Pattern Recognition Q11 of Q15
Bit Manipulation - UTF-8 Validation
You are given a sequence of integers representing bytes. You need to verify if this sequence forms a valid encoding where each character can be 1 to 4 bytes long, and continuation bytes must start with bits '10'. Which approach best guarantees an efficient and correct validation?
AUse a greedy approach that always assumes the longest possible character at each step.
BUse a brute force approach checking each byte with nested conditions for all possible byte patterns.
CUse dynamic programming to store valid prefixes and build up to the full sequence.
DUse a single pass with a counter tracking how many continuation bytes are expected next.
Step-by-Step Solution
Step 1: Understand the problem constraints
The problem requires validating UTF-8 encoding where each character can be 1 to 4 bytes, and continuation bytes must start with '10'.
Step 2: Identify the approach that efficiently tracks continuation bytes
The single pass with a continuation byte counter efficiently tracks how many continuation bytes are expected, ensuring correctness and O(n) time.
Final Answer:
Option D -> Option D
Quick Check:
Single pass with counter matches UTF-8 rules and is optimal [OK]
Quick Trick:Track continuation bytes with a counter for linear validation [OK]
Common Mistakes:
MISTAKES
Assuming greedy longest match always works
Using DP unnecessarily complicates the problem
Trap Explanation:
PITFALL
Greedy or DP approaches seem plausible but fail on partial or invalid continuation bytes.
Interviewer Note:
CONTEXT
Tests if candidate recognizes the pattern and optimal approach for UTF-8 validation.
Master "UTF-8 Validation" in Bit Manipulation
3 interactive learning modes - each teaches the same concept differently
