std::vector<T,Allocator>::capacity

 

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std::vector

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vector::vector vector::~vector vector::operator= vector::assign vector::assign_range (C++23)   vector::get_allocator Element access vector::operator[] vector::at vector::data vector::front vector::back Iterators vector::beginvector::cbegin (C++11) vector::endvector::cend (C++11) vector::rbeginvector::crbegin (C++11) vector::rendvector::crend (C++11)	Capacity vector::empty vector::size vector::max_size vector::reserve vector::capacity vector::shrink_to_fit (DR*) Modifiers vector::clear vector::erase vector::insert vector::insert_range (C++23) vector::append_range (C++23) vector::emplace (C++11) vector::emplace_back (C++11) vector::push_back vector::pop_back vector::resize vector::swap
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operator==operator<=> (C++20) swap(std::vector) erase(std::vector)erase_if(std::vector) (C++20)(C++20)	operator!=operator<operator>operator<=operator>= (until C++20)(until C++20)(until C++20)(until C++20)(until C++20)
Deduction guides(C++17)

 

size_type capacity()const;		(noexcept since C++11) (constexpr since C++20)

Returns the number of elements that the container has currently allocated space for.

Parameters

(none)

Return value

Capacity of the currently allocated storage.

Complexity

Constant.

Example

Run this code

#include <iomanip>#include <iostream>#include <vector>   int main(){int sz =100;std::vector<int> v;   auto cap = v.capacity();std::cout<<"Initial size: "<< v.size()<<", capacity: "<< cap <<'\n';   std::cout<<"\nDemonstrate the capacity's growth policy.""\nSize: Capacity: Ratio:\n"<<std::left;while(sz-->0){ v.push_back(sz);if(cap != v.capacity()){std::cout<<std::setw(7)<< v.size()<<std::setw(11)<< v.capacity()<<std::setw(10)<< v.capacity()/static_cast<float>(cap)<<'\n'; cap = v.capacity();}}   std::cout<<"\nFinal size: "<< v.size()<<", capacity: "<< v.capacity()<<'\n';}

Possible output:

Initial size: 0, capacity: 0   Demonstrate the capacity's growth policy. Size: Capacity: Ratio: 1 1 inf 2 2 2 3 4 2 5 8 2 9 16 2 17 32 2 33 64 2 65 128 2   Final size: 100, capacity: 128

See also

size	returns the number of elements (public member function)
reserve	reserves storage (public member function)