Bit Manipulation - Sum of Two Integers Without + Operator
What is the output of getSum(-2, 3) using the recursive bitwise sum function below?
What is the output of getSum(-2, 3) using the recursive bitwise sum function below?
medium🧾 Code Trace Q4 of Q15
Step-by-Step Solution
Solution:
Step 1: Convert inputs to 32-bit mask
-2 in 32-bit unsigned is 0xFFFFFFFE, 3 is 0x00000003.Step 2: Trace recursive calls
sum_ = (0xFFFFFFFE XOR 3) & MASK = 0xFFFFFFFD, carry = ((0xFFFFFFFE & 3) << 1) & MASK = 4; next call getSum(0xFFFFFFFD, 4)Step 3: Continue until carry is 0
Eventually returns 1, which is the sum of -2 + 3.Final Answer:
Option B -> Option BQuick Check:
-2 + 3 = 1 matches output [OK]
Quick Trick: Masking handles negative numbers correctly [OK]
Common Mistakes:
MISTAKES- Ignoring masking leads to wrong negative results
Trap Explanation:
PITFALL- Candidates often forget to mask or handle sign bits, causing wrong output.
Interviewer Note:
CONTEXT- Tests handling of negative numbers and masking in bitwise sum
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