bitmask c++ code example

Example 1: bit manupulation in c++

Bitwise Operator
//if both are true then true else false
&
//if both are false then false else true
|
//changes true into false and vice-versa
~
//returns true if exactly one is true else false
//checks if both are different
^
//a<<b multiply a with 2 , b times
<<
//a>>b divide a with 2 ,  b times
>>
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check whether a numbe is a power of 2
i.e if it comes in the format 2**n
int x;
cin >>x;
cout<<~(x&(x-1));
-------------------------------------------------
count no of ones in the binary representation of th given number
int count = 1;
while(n!=0){
    count++;
    n = n&(n-1);
}
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check whether the i'th bit is set or not i.e 1
for the binary of number n
if(n & (1<<i) == true){
    cout<<"Yes it is a bit"
}
-------------------------------------------------

Example 2: bitmask c++

- Set ith bit:    x|(1<<i)
   1100 1100
|  0001 0000    (1<<i)
  -----------
   1101 1100  
  
- Get ith bit:    (x&(1<<i) != 0)
    0010 1100
&   0010 0000   (1<<i)
  ------------
    0010 0000   (is not zero)

- Clear ith bit:   x&(~(1<<i))
                      ~ : inverts
   0011 0110
&  1101 1111   ~(1<<i)
  -----------
   0001 0110