Reverse Bits - Building the Result

To reverse the bits, process $n$ from right to left (using $n \& 1$ to get the current bit, then shifting $n$ right). Simultaneously build the result from left to right (shifting the result left and adding the new bit).

Initialize $result = 0$. For each of the 32 bits: shift $result$ left by 1 (making room for the next bit), extract the rightmost bit of $n$ using $n \& 1$, add that bit to $result$ using OR ($|$), then shift $n$ right by 1.

After 32 iterations, you have processed all bits of $n$ and built the reversed result. The key is synchronizing two shifts: left for the result, right for the input.