Bit Manipulation - Counting Bits (0 to N)
Given the output array [0, 1, 1, 2, 1, 2, 2, 3], which represents the count of set bits for numbers from 0 to n, what is the value of n?
Given the output array [0, 1, 1, 2, 1, 2, 2, 3], which represents the count of set bits for numbers from 0 to n, what is the value of n?
hard🔄 Reverse Engineer Q9 of Q15
Step-by-Step Solution
Solution:
Step 1: Count length of output array
Array length is 8, so numbers from 0 to 7.Step 2: Confirm last index corresponds to n=7
Output matches counts for 0 to 7.Final Answer:
Option D -> Option DQuick Check:
Array length minus one equals n [OK]
Quick Trick: Output length = n + 1 for counting bits [OK]
Common Mistakes:
MISTAKES- Confusing array length with n
- Off-by-one errors
- Misreading counts as input values
Trap Explanation:
PITFALL- Candidates often mistake output length for n or misinterpret counts as inputs.
Interviewer Note:
CONTEXT- Tests ability to reverse engineer input from DP output
Master "Counting Bits (0 to N)" in Bit Manipulation
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