C# Program for Count set bits in an integer

Last Updated : 02 Jan, 2019

Write an efficient program to count number of 1s in binary representation of an integer.

Examples :

Input : n = 6
Output : 2
Binary representation of 6 is 110 and has 2 set bits

Input : n = 13
Output : 3
Binary representation of 11 is 1101 and has 3 set bits

setbit

Recommended: Please solve it on “PRACTICE ” first, before moving on to the solution.

1. Simple Method Loop through all bits in an integer, check if a bit is set and if it is then increment the set bit count. See below program.

C#

// C# program to Count set 
// bits in an integer 
using System; 
  
class GFG { 
    // Function to get no of set 
    // bits in binary representation 
    // of positive integer n 
    static int countSetBits(int n) 
    { 
        int count = 0; 
        while (n > 0) { 
            count += n & 1; 
            n >>= 1; 
        } 
        return count; 
    } 
  
    // Driver Code 
    public static void Main() 
    { 
        int i = 9; 
        Console.Write(countSetBits(i)); 
    } 
} 
  
// This code is contributed by Sam007 

Output:

Recursive Approach :

C#

// C# implementation of recursive 
// approach to find the number of 
// set bits in binary representation 
// of positive integer n 
using System; 
  
class GFG { 
  
    // recursive function 
    // to count set bits 
    public static int countSetBits(int n) 
    { 
  
        // base case 
        if (n == 0) 
            return 0; 
  
        else
  
            // if last bit set 
            // add 1 else add 0 
            return (n & 1) + countSetBits(n >> 1); 
    } 
  
    // Driver code 
    static public void Main() 
    { 
  
        // get value 
        // from user 
        int n = 9; 
  
        // function calling 
        Console.WriteLine(countSetBits(n)); 
    } 
} 
  
// This code is contributed by aj_36 