std::bitset<N>::count
From cppreference.com
std::size_t count() const;
|
(noexcept since C++11) (constexpr since C++23) |
|
Returns the number of bits that are set to true.
Return value
Number of bits that are set to true.
Example
Run this code
#include <bitset>
#include <iostream>
constexpr auto popcount(unsigned x) noexcept
{
unsigned num{};
for (; x; ++num, x &= (x - 1));
return num;
}
static_assert(popcount(0b101010) == std::bitset<8>{0b101010}.count());
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
See also
| returns the number of bits that the bitset holds (public member function) | |
(C++20) |
counts the number of 1 bits in an unsigned integer (function template) |
