Find the Number of 1 Bits in a large Binary Number in C++

Given a 32-bit Unsigned Binary Number, the task is to count the set bits, i.e., '1's present in it.

For Example


N = 00000000000000100111



Explanation: Total set bits present in the given unsigned number is 4, thus we will return the output as '4'.

Approach to Solve this Problem

We have given an unsigned 32-bit binary number. The task is to count how many '1's present in it.

To count the number of '1's present in the given binary number, we can use the inbuilt STL function '__builin_popcount(n)' which takes a binary number as the input parameter.

  • Take a binary number N as the input.
  • A function count1Bit(uint32_t n) takes a 32-bit binary number as the input and returns the count of '1' present in the binary number.
  • The inbuilt function __builtin_popcount(n) takes the input of 'n' as a parameter and returns the count.


Live Demo

using namespace std;
int count1bits(uint32_t n) {
   return bitset < 32 > (n).count();
int main() {
   uint32_t N = 0000000010100000011;
   cout << count1bits(N) << endl;
   return 0;

Running the above code will generate the output as,



In the given number, there are 4 set bits or '1s' present in it. So, the output is '4'.