Summary of common usage of C++ bit operations

This article summarizes the common usage of C++ bit operations in the form of examples. Share with you for your reference. Specific methods are as follows:

In C++, there are six basic operators for bitwise operations.

The not     ~
shift     < <   > >
with           &
Exclusive or     ^
or           |

Common usage:

1 to determine the even number, the lowest order is 0 or 1, faster than the modulus

x % 2 != 0    //X plus or minus; Instead of saying x%2 is equal to 1, because if x is negative odd, x%2 is equal to negative 1
x & 0x1 == 0 

2 switch two Numbers, no intermediate variables

void mySwap(int &a, int &b)
{
  if(a == b)  //You can get the right answer if you're equal, but you don't have to
    return;

  a ^= b;
  b ^= a;
  a ^= b;
}

Figure out the number of 1's in the binary representation of integers without shifting them one by one

int numOfBit1(int a)
{
  int cnt = 0;
  while(a != 0)
  {
  　　++cnt;
  　　a &= a - 1;  //Put the rightmost 1 as 0; Both positive and negative Numbers can be calculated, negative Numbers are calculated according to the complement, and the last sign bit is also counted
  }
  return cnt;
}

4 + / - conversion, no sign. Whether it's positive or negative, you just take the inverse and add 1

int a = 1;
a = ~a + 1;  //A - 1
a = ~a + 1;  //A becomes 1 again

Take the absolute value, no positive or negative, no sign, return the absolute value

int myAbs(int a)
{
  int sign = a >> 31;    //If a is positive, sign is 0; Otherwise sign is negative 1, which is 0xFFFFFFFF
  return (a^sign) - sign;  //A to the 0 minus 0 is a, a to the minus 1 minus minus 1 is minus a plus 1 is minus a, a to the minus 1 is minus a
}

Hope that this article is helpful for you C++ programming.