Count set bits in an integer in C++

We are given an integer number let’s say, num and the task is to firstly calculate the binary digit of a number and then calculate the total set bits of a number.

Set bits in a binary number is represented by 1. Whenever we calculate the binary number of an integer value then it is formed as the combination of 0’s and 1’s. So, the digit 1 is known as set bit in the terms of the computer.

Input − int number = 50

Output − Count of total set bits in a number are − 3

Explanation − Binary representation of a number 50 is 110010 and if we calculate it in 8-digit number then two 0’s will be appended in the beginning. So, the total set bits in a number are 3.

Input − int number = 10

Output − Count of total set bits in a number are − 2

Explanation − Binary representation of a number 10 is 00001010 and if we calculate it in 8-digit number then four 0’s will be appended in the beginning. So, the total set bits in a number are 2.

Approach used in the below program is as follows

• Input the number in a variable of integer type

• Declare a variable count to store the total count of set bits of type unsigned int

• Start loop FOR from i to 1<<7 and i > 0 and i to i / 2

• Inside the loop, check num & 1 == TRUE then print 1 else print 0

• Start loop while to calculate the total count of bits till number isn’t 0

• Inside the loop, set count = count + number & 1 and also set number >>=1

• Print the count

Example

 Live Demo

#include<iostream>
using namespace std;
//Count total set bits in a number
unsigned int bits(unsigned int number){
   unsigned int count = 0;
   unsigned i;
   //display the total 8-bit number
   cout<<"8-bit digits of "<<number<<" is: ";
   for (i = 1 << 7; i > 0; i = i / 2){
      (number & i)? cout<<"1": cout<<"0";
   }
   //calculate the total set bits in a number
   while (number){
      count += number & 1;
      number >>= 1;
   }
   cout<<"\nCount of total set bits in a number are: "<<count;
}
int main(){
   int number = 50;
   bits(number);
   return 0;
}

Output

If we run the above code it will generate the following output −

8-bit digits of 50 is: 00110010
Count of total set bits in a number are: 3