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/*
 We have to count the number of 1 an integer n has in its binary representation.
 Key concepts:
 - When we perform a bitwise operation it is executed in the bit level.
 - Withwise operations involved: & and =>> <<== (shift right and shift left)
    - 1: 00000000000(..)1
    - shift left performed: 000000(...)10
    */
    
    
   public int hammingWeight(int n) {
       
        //Integer is 32 bits long
        int mask = 1;
        int count = 0;
        for (int i = 0; i < 32; i++) {
            if ((n & mask) != 0)
                count++;
            mask <<= 1;
        }
        
        return count;
    }
    
  /*
 - SECON APPROACH:
    - The key concept here is to understand that n&(n-1) converts the least significant 1 bit in n to 0
    - 8: n   -> 01001000
    - 7: n-1 -> 01000111
    - Result of AND: 010000000
    - So as long as n is not 0 we keep performing this new trick
*/

  public int hammingWeight(int n) {
       
        //Integer is 32 bits long
        int count = 0;
        while (n != 0) {
            count++;
            n &= (n - 1);
        }  
        return count;
    }