num_bits.cc

#include <iostream>
#include <cstdlib>

int num_bits2(long n) {
  int i = 0;
  for(i = 0; n; i++)
   n &= n - 1;  
  return i;
}

int num_bits(long n) {
  int i = 0;
  for(;n;) {
    i += n%2;
    n /= 2;
  }

  return i;
}

int main(int argc, char **argv) {
  std::cout << num_bits(std::atoi(argv[1])) << std::endl;
  std::cout << num_bits2(std::atoi(argv[1])) << std::endl;
  return 0;
}