Common usage of C + + bit operations Summary _c language

In this paper, the common usage of C + + bit operation is summarized with the example form. Share for everyone to use for reference. The specific methods are as follows:

There are 6 basic operators in the C + + bitwise operation, which are, by priority:

Take the Counter ~
Shift << >>
and &
Different or ^
or |

Common uses are:

1 to judge even, the lowest bit is 0 or 1 can be, faster than the model

X 2!= 0    //x positive and negative can be judged; do not x%2 = = 1, because if X is negative odd, X%2=-1
x & 0x1 = 0 

2 Exchange two numbers without intermediate variables

void Myswap (int &a, int &b)
{
  if (a = = b)  //equal can also get the correct result, but no need to return
    ;

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

3 to find the number of 1 in the binary representation of an integer, without a single shift to judge

int numOfBit1 (int a)
{
  int cnt = 0;
  while (a!= 0)
  {
  ++cnt;
  A &= A-1;  The rightmost 1 is set to 0, both positive and negative are calculated, negative numbers are calculated according to the complement, and the last sign bit is also counted
  } return
  cnt;
}

4 positive and negative conversion, do not use the sign. No matter positive or negative, add 1 to the back

int a = 1;
A = ~a + 1;  A becomes-1
a = ~a + 1;  A turns 1 again.

5 absolute value, do not judge positive numbers, do not use positive and negative, return absolute value

int myabs (int a)
{
  int sign = a >>;    If a is positive, sign is 0, otherwise sign is-1, or 0xFFFFFFFF return
  (a^sign)-sign;  (a^0)-0 = A, (a^-1)-( -1) = ~a+1 =-A, a^-1 is a take-back
}

I hope this article will help you with the learning of C + + programming.