std::bitset<N>::count (3) - Linux Manuals

std::bitset<N>::count: std::bitset<N>::count

NAME

std::bitset<N>::count - std::bitset<N>::count

Synopsis

std::size_t count() const; (until C++11)
std::size_t count() const noexcept; (since C++11)

Returns the number of bits that are set to true.

Parameters

(none)

Return value

number of bits that are set to true.

Example

// Run this code

  #include <iostream>
  #include <bitset>

  int main()
  {
      std::bitset<8> b("00010010");
      std::cout << "initial value: " << b << '\n';

      // find the first unset bit
      std::size_t idx = 0;
      while (idx < b.size() && b.test(idx)) ++idx;

      // continue setting bits until half the bitset is filled
      while (idx < b.size() && b.count() < b.size()/2) {
          b.set(idx);
          std::cout << "setting bit " << idx << ": " << b << '\n';
          while (idx < b.size() && b.test(idx)) ++idx;
      }

  }

Output:

  initial value: 00010010
  setting bit 0: 00010011
  setting bit 2: 00010111