From cppreference.com
Defined in header
template<classT>constexprintpopcount(Tx)noexcept;(since C++20)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, unsignedchar, unsignedshort, unsignedint, unsignedlong, unsignedlonglong, or an extended unsigned integer type).
Parameters
x - value of unsigned integer type Return value
The number of 1 bits in the value of x.
Notes
The name popcount is a contraction for “population count”.
macroValueStdFeature
(C++20)
Example
Run this code
#include<bit>#include<bitset>#include<cstdint>#include<iostream>static_assert(std::popcount(0xFULL)==4);intmain(){for(conststd::uint8_tx:{0,0b00011101,0b11111111})std::cout<<"popcount( "<<std::bitset<8>(x)<<" ) = "<<std::popcount(x)<<'\n';}Output:
popcount( 00000000 ) = 0 popcount( 00011101 ) = 4 popcount( 11111111 ) = 8 See also
(C++20)
counts the number of consecutive 0 bits, starting from the most significant bit
(function template)
(C++20)
counts the number of consecutive 1 bits, starting from the most significant bit
(function template)
(C++20)
counts the number of consecutive 0 bits, starting from the least significant bit
(function template)
(C++20)
counts the number of consecutive 1 bits, starting from the least significant bit
(function template)
(C++20)
checks if a number is an integral power of 2
(function template)
returns the number of bits set to true
(public member function of std::bitset<N>)
checks if all, any or none of the bits are set to true
(public member function of std::bitset<N>)