vector::capacity


public member function
size_type capacity () const;

Return size of allocated storage capacity

Returns the size of the allocated storage space for the elements of the vector container.

Notice that, in vectors, the capacity is not necessarily equal to the number of elements that conform the underlying vector content (this can be obtained with member vector::size), but the capacity of the actual allocated space, which is either equal or greater than the content size.

Notice also that this capacity does not suppose a limit to the size of the vector. If more space is required to accomodate new elements in the vector, the capacity is automatically expanded, or can even be explicitly modified by calling member vector::reserve.

The real limit on the size a vector object can reach is returned by member vector::max_size.

Parameters

none

Return Value

The size of the currently allocated storage capacity in the vector, measured in the number elements it could hold.

Member type size_type is an unsigned integral type.

Example

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// comparing size, capacity and max_size
#include <iostream>
#include <vector>
using namespace std;

int main ()
{
  vector<int> myvector;

  // set some content in the vector:
  for (int i=0; i<100; i++) myvector.push_back(i);

  cout << "size: " << (int) myvector.size() << "\n";
  cout << "capacity: " << (int) myvector.capacity() << "\n";
  cout << "max_size: " << (int) myvector.max_size() << "\n";
  return 0;
}


A possible output for this program could be:
size: 100
capacity: 141
max_size: 1073741823


Complexity

Constant.

See also

vector::reserve Request a change in capacity (public member function)
vector::size Return size (public member function)
vector::max_size Return maximum size (public member function)
vector::resize Change size (public member function)