Bit Manipulation - Sum of Two Integers Without + Operator
Given the intermediate state sum_ = 0xFFFFFFFD and carry = 4 in the recursive bitwise sum, what were the original inputs a and b?
Given the intermediate state sum_ = 0xFFFFFFFD and carry = 4 in the recursive bitwise sum, what were the original inputs a and b?
hard🔄 Reverse Engineer Q9 of Q15
Step-by-Step Solution
Solution:
Step 1: Recall sum_ = (a XOR b) & MASK and carry = ((a AND b) << 1) & MASK
Given sum_ and carry, original a and b satisfy these equations.Step 2: Recognize sum_ and carry are intermediate results, so a and b are sum_ and carry from previous call
Thus, a = 0xFFFFFFFD, b = 4.Final Answer:
Option B -> Option BQuick Check:
Intermediate sum_ and carry correspond to inputs for next recursion [OK]
Quick Trick: Intermediate sum_ and carry become next inputs [OK]
Common Mistakes:
MISTAKES- Confusing intermediate results with original inputs
Trap Explanation:
PITFALL- Candidates mistake intermediate XOR and carry as final inputs.
Interviewer Note:
CONTEXT- Tests deep understanding of recursive state transitions
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