Reverse Bits of a Number in DSA Python - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does it mean to reverse the bits of a number?

Reversing the bits of a number means flipping the order of its binary digits from left to right. For example, if the binary is 1011, reversing it gives 1101.

beginner

How many bits do we usually consider when reversing bits of a number?

We usually consider a fixed number of bits, like 32 bits for standard integers, to keep the reversed number consistent in size.

intermediate

What is the first step in reversing bits of a number using code?

The first step is to extract the least significant bit (rightmost bit) using bitwise AND with 1, then shift the reversed number to the left and add the extracted bit to build the reversed number.

intermediate

Why do we shift the reversed number to the left during the bit reversal process?

We shift the reversed number left to make space for the next bit from the original number, effectively building the reversed bit sequence from left to right.

intermediate

What is the time complexity of reversing bits of a fixed-size integer?

The time complexity is O(1) because the number of bits is fixed (like 32 or 64), so the operation takes constant time regardless of the number's value.

What operation extracts the rightmost bit of a number?

A Bitwise OR with 1

B Bitwise AND with 1

C Left shift by 1

D Right shift by 1

Bitwise AND with 1 isolates the least significant bit (rightmost bit) of a number.

If the binary of a number is 1100, what is the reversed bit sequence?

A 0011

B 1100

C 1001

D 0110

Reversing 1100 gives 0011 by flipping the bits order.

Why do we shift the original number to the right during bit reversal?

A To double the number

B To add a new bit

C To reverse the bits automatically

D To remove the bit already processed

Shifting right removes the least significant bit that was already extracted.

What is the size of bits usually considered for reversing bits in a 32-bit integer?

A 16 bits

B 64 bits

C 32 bits

D 8 bits

A 32-bit integer has 32 bits, so we reverse all 32 bits.

What is the final step after processing all bits in bit reversal?

A Return the reversed number

B Shift the reversed number right

C Add 1 to the reversed number

D Multiply the reversed number by 2

After processing all bits, we return the reversed number as the result.

Explain the step-by-step process to reverse the bits of a 32-bit number.

Think about how you build the reversed number bit by bit.

Why is reversing bits useful in computer science or programming?

Consider areas where binary data order matters.