# Count unset bits of a number in C++

C++Server Side ProgrammingProgramming

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 unset bits of a number.

Unset bits in a binary number is represented by 0. 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 0 is known as unset bit in the terms of the computer.

Input − int number = 50

Output − Count of total unset 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 unset bits in a number are 3.

Input − int number = 10

Output − Count of total unset bits in a number are: 6

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 unset bits in a number are 6.

## 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

• Inside the loop, increment the value of total digits in a number.

• 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

• Set count as total digits in a number - total set bits in a number.

• Print the count

## Example

Live Demo

#include<iostream>
using namespace std;
//Count total unset bits in a number
unsigned int unset_bits(unsigned int number){
unsigned int total_digits = 0;
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";
total_digits++;
}
//calculate the total unset bits in a number
while (number){
count += number & 1;
number >>= 1;
}
count = total_digits - count;
cout<<"\nCount of total unset bits in a number are: "<<count;
}
int main(){
int number = 50;
unset_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: 5
Updated on 31-Oct-2020 05:52:23