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What is the time complexity of the recursive bitwise sum algorithm for adding two integers a and b without using the + operator, assuming 32-bit integers?

medium🪤 Complexity Trap Q13 of Q15
Bit Manipulation - Sum of Two Integers Without + Operator
What is the time complexity of the recursive bitwise sum algorithm for adding two integers a and b without using the + operator, assuming 32-bit integers?
AO(1) constant time since integers are fixed size
BO(log(max(a,b))) due to the number of bits processed
CO(n), where n is the sum of a and b
DO(n^2) because each recursion does bitwise operations on all bits
Step-by-Step Solution
Solution:
  1. Step 1: Fixed integer size implies constant time

    Since integers are 32-bit fixed size, the number of operations is bounded by a constant.
  2. Step 2: Recursion depth and bitwise operations are limited

    Maximum recursion depth and bitwise operations are limited by fixed bit width, so complexity is O(1).
  3. Final Answer:

    Option A -> Option A
  4. Quick Check:

    Fixed 32-bit integers mean constant time complexity [OK]
Quick Trick: Fixed integer size means constant time complexity [OK]
Common Mistakes:
MISTAKES
  • Confusing input magnitude with bit length
  • Assuming complexity depends on numeric value
  • Thinking recursion depth varies with input size
Trap Explanation:
PITFALL
  • Though bit length affects complexity theoretically, fixed 32-bit integers mean constant time in practice.
Interviewer Note:
CONTEXT
  • Tests understanding of complexity with fixed-size integers versus variable input size.
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