Bit manipulations

1. Multiply two Numbers Without Using * Operator

m=0;
          while (a)
          {
                if (a&1)
                   m+=b;
                a>>=1;
                b<<=1;
          }
          return m;

1. check number is even or odd

   http://www.programmingsimplified.com/c/source-code/c-program-check-odd-even

2. check if a num is power of 2

    public class Solution {
    public boolean isPowerOfTwo(int n) {
        if(n<=0) 
        return false;
   
        while(n>2){
            int t = n>>1;
            int c = t<<1;
   
            if(n-c != 0)
                return false;
   
            n = n>>1;
        }
   
        return true;
    }
   }
   

   solution II:

    public class Solution {
    public boolean isPowerOfTwo(int n) {
        if(n<=0) 
            return false;
        return ((n & n-1) == 0);
    }
   }
   

3. check a number is positive or negative

   int k = (a >> 31) & 1; k == 1 negative, k == 0 positive

4. find max of two numbers without comparison

   check Cracking coding interview at page 476

int findMax( int x, int y)
{
   int z = x - y;
   int i  = (z  >>  31)  &  0x1;
   int  max  =  x - i  *  z;
   return max;
}