vector::size y vector::capacity
Muestra cómo utilizar vector:: tamaño y las funciones de la biblioteca estándar de la plantilla (STL) de vector:: capacidad en Visual C++.
template<class _TYPE, class _A>
void vector::reserve(
size_type _N
);
template<class _TYPE, class _A>
size_type vector::max_size( ) const;
template<class _TYPE, class _A>
void vector::resize(
size_type _N,
_TYPE _X = _TYPE( )
);
template<class _TYPE, class _A>
size_type vector::capacity( ) const;
template<class _TYPE, class _A>
size_type vector::size( ) const;
Comentarios
[!NOTA]
La clase y los nombres de parámetro en el prototipo no coincide con la versión del archivo de encabezado.Algunos se han modificado para mejorar la legibilidad.
el ejemplo declara un vector vacío de enteros.Agrega un solo elemento entero al vector, y después muestra información sobre el tamaño, el tamaño máximo, y la capacidad de vector.Reserva el almacenamiento para 1.000 elementos y genera la misma información sobre el vector.Finalmente, cambia el tamaño del vector a 2.000 elementos y muestra la información.
Ejemplo
// Remax.cpp
// compile with: /EHsc
// Illustrates vector::reserve, vector::max_size,
// vector::resize, vector::resize, and vector::capacity.
//
// Functions:
//
// vector::max_size - Returns maximum number of elements vector could
// hold.
//
// vector::capacity - Returns number of elements for which memory has
// been allocated.
//
// vector::size - Returns number of elements in the vector.
//
// vector::resize - Reallocates memory for vector, preserves its
// contents if new size is larger than existing size.
//
// vector::reserve - Allocates elements for vector to ensure a minimum
// size, preserving its contents if the new size is
// larger than existing size.
//
// vector::push_back - Appends (inserts) an element to the end of a
// vector, allocating memory for it if necessary.
//
//////////////////////////////////////////////////////////////////////
// The debugger cannot handle symbols more than 255 characters long.
// STL often creates symbols longer than that.
// When symbols are longer than 255 characters, the warning is disabled.
#pragma warning(disable:4786)
#include <iostream>
#include <vector>
using namespace std ;
typedef vector<int> INTVECTOR;
int main()
{
// Dynamically allocated vector begins with 0 elements.
INTVECTOR theVector;
// Add one element to the end of the vector, an int with the value 42.
theVector.push_back(42) ;
// Show statistics about vector.
cout << "theVector's size is: " << theVector.size() << endl;
cout << "theVector's maximum size is: " << theVector.max_size()
<< endl;
cout << "theVector's capacity is: " << theVector.capacity() << endl;
// Ensure there's room for at least 1000 elements.
theVector.reserve(1000);
cout << endl << "After reserving storage for 1000 elements:" << endl;
cout << "theVector's size is: " << theVector.size() << endl;
cout << "theVector's maximum size is: " << theVector.max_size()
<< endl;
cout << "theVector's capacity is: " << theVector.capacity() << endl;
// Ensure there's room for at least 2000 elements.
theVector.resize(2000);
cout << endl << "After resizing storage to 2000 elements:" << endl;
cout << "theVector's size is: " << theVector.size() << endl;
cout << "theVector's maximum size is: " << theVector.max_size()
<< endl;
cout << "theVector's capacity is: " << theVector.capacity() << endl;
}
Resultados del ejemplo
El resultado siguiente es para x86.
theVector's size is: 1
theVector's maximum size is: 1073741823
theVector's capacity is: 1
After reserving storage for 1000 elements:
theVector's size is: 1
theVector's maximum size is: 1073741823
theVector's capacity is: 1000
After resizing storage to 2000 elements:
theVector's size is: 2000
theVector's maximum size is: 1073741823
theVector's capacity is: 2000
Requisitos
encabezado: <vector>