Usare le funzioni STL vector::erase, vector::empty e vector::p ush_back in Visual C++

Questo articolo illustra come usare la vector::erase funzione, la vector::empty funzione e le vector::push_back funzioni STL (Standard Template Library) in Visual C++. Le informazioni si applicano solo al codice Visual C++ non gestito.

Versione originale del prodotto: Visual C++
Numero KB originale: 158612

Intestazione obbligatoria

<vector>

Prototipi

template<class _TYPE, class _A>
void vector::push_back(const _TYPE& X);

template<class _TYPE, class _A>
iterator vector::erase(iterator Iterator);

template<class _TYPE, class _A>
iterator vector::erase(iterator First, iterator Last);

template<class _TYPE, class _A>
bool vector::empty() const;

Descrizione

L'esempio dichiara un vettore vuoto di interi. Aggiunge 10 interi al vettore, quindi visualizza il contenuto del vettore. Elimina il sesto elemento usando la cancellazione e quindi visualizza nuovamente il contenuto del vettore. Elimina il resto degli elementi usando una forma diversa di cancellazione, quindi visualizza nuovamente il vettore (ora vuoto). La ShowVector routine usa la funzione vuota per determinare se generare il contenuto del vettore.

Codice di esempio

In Visual C++ .NET e in Visual C++, /EHsc è impostato per impostazione predefinita ed è equivalente a /GX.

//////////////////////////////////////////////////////////////////////
// Compile options needed: /GX
// Empty.cpp -- Illustrates the vector::empty and vector::erase
// functions.
// Also demonstrates the vector::push_back function.
// Functions:
// vector::empty - Returns true if vector has no elements.
// vector::erase - Deletes elements from a vector (single & range).
// vector::begin - Returns an iterator to start traversal of the
// vector.
// vector::end - Returns an iterator for the last element of the
// vector.
// vector::push_back - Appends (inserts) an element to the end of a
// vector, allocating memory for it if necessary.
// vector::iterator - Traverses the vector.
// of Microsoft Corporation
// Copyright (c) 1996 Microsoft Corporation. All rights reserved.
//////////////////////////////////////////////////////////////////////
// The debugger can't 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>

#if _MSC_VER > 1020 // if VC++ version is > 4.2
    using namespace std; // std c++ libs implemented in std
#endif

typedef vector<int, allocator<int> > INTVECTOR;

const ARRAY_SIZE = 10;

void ShowVector(INTVECTOR &theVector);

void main()
{
     // Dynamically allocated vector begins with 0 elements.
     INTVECTOR theVector;

     // Intialize the vector to contain the numbers 0-9.
     for (int cEachItem = 0; cEachItem < ARRAY_SIZE; cEachItem++)
         theVector.push_back(cEachItem);

     // Output the contents of the dynamic vector of integers.
     ShowVector(theVector);

     // Using void iterator erase(iterator Iterator) to
     // delete the 6th element (Index starts with 0).
     theVector.erase(theVector.begin() + 5);

     // Output the contents of the dynamic vector of integers.
     ShowVector(theVector);

     // Using iterator erase(iterator First, iterator Last) to
     // delete a range of elements all at once.
     theVector.erase(theVector.begin(), theVector.end());

     // Show what's left (actually, nothing).
     ShowVector(theVector);
}

// Output the contents of the dynamic vector or display a
// message if the vector is empty.
void ShowVector(INTVECTOR &theVector)
{
     // First see if there's anything in the vector. Quit if so.
     if (theVector.empty())
     {
         cout << endl << "theVector is empty." << endl;
         return;
     }

     // Iterator is used to loop through the vector.
     INTVECTOR::iterator theIterator;

     // Output contents of theVector.
     cout << endl << "theVector [ " ;
     for (theIterator = theVector.begin(); theIterator != theVector.end();
     theIterator++)
     {
         cout << *theIterator;
         if (theIterator != theVector.end()-1) cout << ", ";
         // cosmetics for the output
     }
     cout << " ]" << endl ;
}

Output del programma:

theVector [ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 ]
theVector [ 0, 1, 2, 3, 4, 6, 7, 8, 9 ]
theVector is empty.

Riferimenti

vector::empty, vector::erase e vector::p ush_back