bitcount in c+++

// CPP program to illustrate the 
// bitset::count() function 
// when the input is an integer 
#include <bits/stdc++.h> 
using namespace std; 
  
int main() 
{ 
    // Initialisation of a bitset 
    bitset<4> b1(16); 
    bitset<4> b2(18); 
  
    // Function to count the 
    // number of set bits in b1 
    int result1 = b1.count(); 
    cout << b1 << " has " << result1 
         << " set bit\n"; 
  
    // Function to count the 
    // number of set bits in b2 
    int result2 = b2.count(); 
    cout << b2 << " has " << result2 
         << " set bit"; 
  
    return 0; 
}