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

Recall & Review

beginner

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

Reversing the bits means flipping the order of all bits in the binary form of the number, so the first bit becomes the last, the second becomes the second last, and so on.

beginner

How many bits are typically considered when reversing bits of an integer in C?

Usually 32 bits are considered for a standard unsigned int in C, but it depends on the system and the integer size.

beginner

What is the purpose of using bitwise AND (&) with 1 in bit reversal?

Bitwise AND with 1 extracts the least significant bit (rightmost bit) of the number, which is used to get each bit one by one during reversal.

intermediate

Explain the role of left shift (<<) in the bit reversal process.

Left shift moves bits to the left, making space for the next bit to be added at the right end of the reversed number.

intermediate

Why do we right shift (>>) the original number during bit reversal?

Right shifting the original number moves the next bit to the least significant position so it can be extracted and added to the reversed number.

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

A Right shift the reversed number

B Extract the least significant bit using & 1

C Left shift the number by 1

D Add 1 to the number

We start by extracting the least significant bit to add it to the reversed number.

How many times do you repeat the bit extraction and shifting to reverse a 32-bit number?

A 8 times

B 16 times

C 32 times

D 64 times

You repeat the process 32 times to cover all bits in a 32-bit number.

What does the left shift operator (<<) do in the reversed number during bit reversal?

A Moves bits to the right

B Resets bits

C Extracts bits

D Moves bits to the left

Left shift moves bits to the left to make space for the next bit.

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

A To discard the least significant bit after processing

B To add bits to the reversed number

C To reset the reversed number

D To multiply the number

Right shifting discards the bit already processed and brings the next bit to the least significant position.

If the input number is 13 (binary 00000000000000000000000000001101), what is the reversed 8-bit output?

A 10110000 (decimal 176)

B 10110000 (decimal 13)

C 00001101 (decimal 13)

D 11010000 (decimal 208)

Reversing bits of 00001101 gives 10110000 which is decimal 176.

Describe the step-by-step process to reverse the bits of a 32-bit unsigned integer.

Think about how you move bits from the original number to the reversed number one by one.

Explain why bitwise operations are efficient for reversing bits compared to string or array methods.

Consider how computers handle bits natively.