Print Bitwise AND Set of a Number n in C++

In this problem, we have to print all the numbers from 0 to n which are Bitwise AND of a binary of n.

Let’s take an example to understand the concept better.

Input : N = 4.
Output : 0 4
Explanation :
   0 & 4 = 0
   1 & 4 = 0
   2 & 4 = 0
   3 & 4 = 0
   4 & 4 = 4.
Input : N = 6
Output : 0, 2, 4, 6

To solve this problem, we need to use bitwise operators. Using these we will find the required subsets. We will iterate backward from n to 1 using a different update function that will use only those values that return are outputs of and operation of some AND with n. The operation would be i = (i-1) & N.

Based on this idea lets create an algorithm −

Algorithm

Step 1 : Loop from n to 1 using decrement operator i = (i-1) & n
Step 2 : PRINT i.
Step 3 : EXIT.

Example

Program implementation of the above algorithm −

 Live Demo

#include <iostream>
using namespace std;
int main() {
   int n = 11;
   for (int i = n; i > 0; i = (i - 1) & n)
      cout << i << " ";
   cout << 0;
   return 0;
}

Output

11 10 9 8 3 2 1 0