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std::bitset<N>::count

From cppreference.com
< cpp‎ | utility‎ | bitset
 
 
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std::size_t count() const;
(until C++11)
std::size_t count() const noexcept;
(since C++11)
(constexpr since C++23)

Returns the number of bits that are set to true.

Contents

[edit] Parameters

(none)

[edit] Return value

number of bits that are set to true.

[edit] Example

#include <bitset>
#include <iostream>
 
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

[edit] See also

returns the number of bits that the bitset holds
(public member function) [edit]
(C++20)
counts the number of 1 bits in an unsigned integer
(function template) [edit]