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(until C++20) | ||||
| Element access | ||||
bitset::count | ||||
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(C++11) | ||||
std::size_t count()const; | (noexcept since C++11) (constexpr since C++23) | |
Returns the number of bits that are set totrue.
Number of bits that are set totrue.
#include <bitset>#include <iostream> constexprauto 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 bitstd::size_t idx=0;while(idx< b.size()&& b.test(idx))++idx; // Continue setting bits until half the bitset is filledwhile(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: 00010010Setting bit 0: 00010011Setting bit 2: 00010111
| returns the number of bits that the bitset holds (public member function)[edit] | |
(C++20) | counts the number of1 bits in an unsigned integer (function template)[edit] |
