template< class T >
constexpr int popcount( T x ) noexcept;
Returns the number of 1 bits in the value of x.
This overload participates in overload resolution only if T
is an unsigned integer type (that is, unsigned char, unsigned short, unsigned int, unsigned long, unsigned long long, or an extended unsigned integer type).
The number of 1 bits in the value of x.
[edit] NotesThe name popcount
is a contraction for âpopulation countâ.
#include <bit> #include <bitset> #include <cstdint> #include <iostream> static_assert(std::popcount(0xFULL) == 4); int main() { for (const std::uint8_t x : {0, 0b00011101, 0b11111111}) std::cout << "popcount( " << std::bitset<8>(x) << " ) = " << std::popcount(x) << '\n'; }
Output:
popcount( 00000000 ) = 0 popcount( 00011101 ) = 4 popcount( 11111111 ) = 8[edit] See also counts the number of consecutive â0â bits, starting from the most significant bit
std::bitset<N>
) [edit] checks if all, any or none of the bits are set to true
std::bitset<N>
) [edit]
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