Reverse Bits

PROBLEM

Reverse bits of a given 32 bits unsigned integer.

SOLVING

We’ll use Bit Manipulation method

Steps

Create a uint32_t result we’ll return as the answer
Repeat 32 time or the longer of your bit
- result equal to result or (| or bit operation) on the result of n and (& and bit operation) 1 to get the first bit

Example

Example with 6bit (32 is tooooo long) 011101

=n=      [011101] & 1 == 1
=result= [000000] << 1
=n=      [001110] & 1 == 0
=result= [000001] << 0
=n=      [000111] & 1 == 1
=result= [000010] << 1
=n=      [000011] & 1 == 1
=result= [000101] << 1
=n=      [000001] & 1 == 1
=result= [001011] << 1
=n=      [000000] & 1 == 0
=result= [010111] << 0
=result= [101110]

Code

class Solution {
public:
  uint32_t reverseBits(uint32_t n) {
    uint32_t result;

    for (int i = 0; i < 32; i++) {
      result = (result << 1) | (n & 1);
      n >>= 1;
    }
    return result;
  }
};