Editorial

Solution walkthrough

Review the explanation, then compare the reference implementation.

Video explanation

Solution

Intuition

Reversing a fixed-width bit pattern means reading its bits from least significant to most significant and appending them in that order to a new number. Leading zeros in the original pattern still matter: after reversal, they occupy the low-order positions.

Approach

Initialize the result to zero.
Repeat exactly 32 times. Shift the result left once to make room, then append the current input's least significant bit.
Shift the input right once to expose the next bit.
Return the accumulated result. Processing all 32 positions, even after the remaining input becomes zero, preserves the required width instead of reversing only the significant bits.

class Solution:
    def reverseBits(self, n: int) -> int:
        res = 0

        for i in range(32):
            res <<= 1
            res |= (n % 2)
            n >>= 1

        return res

Complexity analysis

The loop always processes exactly 32 bits, so time and auxiliary space are both O(1).