vector::size e vector::capacity
Ilustra como usar o vector::size e vector::capacity funções de biblioteca STL (Standard Template) no 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;
Comentários
.gif "Observação") Observação |
|---|
Nomes de classe/parâmetro o protótipo não coincidem com a versão no arquivo de cabeçalho.Alguns foram modificados para melhorar a legibilidade. |
O exemplo declara um vetor de inteiros de vazio.Ele adiciona um elemento inteiro único para o vetor e, em seguida, mostra informações sobre o tamanho, o tamanho máximo e a capacidade do vetor.Ele reserva-se o armazenamento para 1.000 elementos e exibe as mesmas informações sobre o vetor.Finalmente, redimensiona o vetor de 2.000 elementos e, em seguida, exibe as informações.
Exemplo
// 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;
}
Saída de exemplo
A seguinte saída é 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
Cabeçalho: <vector>