How can I toggle N-bit of integer

Question

I try to toggle the bits of a numeric value by using the ~ complement operator, but it results in a negative number. For example I want toggle 5 -> 2 (101 -> 010)

How can I change this number in Visual Studio?

Answer 1

What you want is the XOR operator ^.

If your original number is x, then:

int y = x ^ 0b111;

Will have the first 3 bits flipped (I supposed that's what you meant by "toggled").

Answer 2

As a 32-bit value, 5 is not 0b101. It is 0b0000'0000'0000'0000'0000'0000'0000'0101.

(Although those leading zeroes are not significant, value-wise, the fact that you are performing bit operations makes the "width" of the binary representation important.)

So, when you flip all the bits, you get 0b1111'1111'1111'1111'1111'1111'1111'1010 which is indeed a negative number per two's complement encoding.

If you just wanted to flip the three least significant bits, you can use a mask to do that:

const int y = x ^ 0b111;

This will leave all the other bits alone.

Answer 3

I prefer this:

number ^= 1UL << N

Answer 4

Thank you I solve this problem.

By Use number ^= 1UL << N Thank you for your Answer.

Answer 5

Hello you can do like this .

(~N)<0 ? (long)pow(2, 32) + ~N : ~N;