View source for Template:cpp/container/capacity

{{cpp/container/{{{1|}}}/title|capacity}}
{{cpp/container/{{{1|}}}/navbar}}
{{dcl begin}}
{{#switch:{{{1|}}}
|vector=
{{dcl|notes={{mark noexcept since c++11}}<br>{{mark constexpr since c++20}}|
size_type capacity() const;
}}
|
}}
{{dcl end}}

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===
{{example
|code=
<!--safety check for potential reuse of this template-->
{{#ifeq:{{{1|}}}|vector|
#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';
}
}}
|p=true
|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===
{{dsc begin}}
{{dsc inc|cpp/container/dsc size|{{{1|}}}}}
{{dsc inc|cpp/container/dsc reserve|{{{1|}}}}}
{{dsc end}}