[Solved] Consider the following Python function that reverses bits of a 32-bit unsigned integer using divide and conquer masks: def reverseBits(n: int) -> int:... | Bit Manipulation

Bit Manipulation - Reverse Bits

Consider the following Python function that reverses bits of a 32-bit unsigned integer using divide and conquer masks:

def reverseBits(n: int) -> int:
    n = ((n >> 1) & 0x55555555) | ((n & 0x55555555) << 1)
    n = ((n >> 2) & 0x33333333) | ((n & 0x33333333) << 2)
    n = ((n >> 4) & 0x0f0f0f0f) | ((n & 0x0f0f0f0f) << 4)
    n = ((n >> 8) & 0x00ff00ff) | ((n & 0x00ff00ff) << 8)
    n = ((n >> 16) | (n << 16)) & 0xffffffff
    return n

print(reverseBits(11))  # Input is 11 (binary 00000000000000000000000000001011)

What is the output of this code?

A2952790016

B3758096384

C2147483648

D3221225472

Step-by-Step Solution

Solution:

Step 1: Convert input to binary
11 in 32-bit binary is 00000000000000000000000000001011.
Step 2: Reverse bits using masks
Reversing bits yields 11010000000000000000000000000000, which is 2952790016 in decimal.
Final Answer:
Option A -> Option A
Quick Check:
Binary reversal matches decimal 2952790016 [OK]

Quick Trick: Reverse bits of 11 -> 2952790016 decimal [OK]

Common Mistakes:

MISTAKES

Confusing left and right shifts
Forgetting to mask final result to 32 bits
Miscounting bit positions

Trap Explanation:

PITFALL

Some candidates confuse the reversed bit pattern with the original or forget masking, leading to wrong decimal output.

Interviewer Note:

CONTEXT

Tests ability to mentally execute bitwise operations and verify correctness.

Master "Reverse Bits" in Bit Manipulation

3 interactive learning modes - each teaches the same concept differently

Try It Solution Trace

More Bit Manipulation Quizzes

Consider the following Python function that reverses bits of a 32-bit unsigned integer using divide and conquer masks:

Step 1: Convert input to binary

Step 2: Reverse bits using masks

Final Answer:

Quick Check:

Want More Practice?