C++ Tutorial/vector/vector back
Accessing the Back of a Vector
<source lang="cpp">#include <iostream>
- include <list>
- include <vector>
using namespace std; template <class ForwIter> void print(ForwIter first, ForwIter last, const char* title) {
cout << title << endl;
while ( first != last)
cout << *first++ << "\t";
cout << endl;
} class Card {
public:
enum Suit { spades, clubs, hearts, diamonds };
Card( int value = 1, Suit suit = spades );
// value - 1 = Ace, 2-10, 11 = Jack, 12 = Queen, 13 = King
int suit() const;
int value() const;
private:
int value_;
Suit suit_;
}; inline Card::Card( int value, Suit suit )
: value_( value ), suit_( suit )
{} // empty inline int Card::suit() const { return suit_; } inline int Card::value() const { return value_; } // global function ostream& operator<<( ostream& out, const Card& card ) {
if( card.value() >= 2 && card.value() <= 10 )
out << card.value();
else
switch( card.value() )
{
case 1: out << "Ace"; break;
case 11: out << "Jack"; break;
case 12: out << "Queen"; break;
case 13: out << "King"; break;
default: out << "Unknown value"; break;
};
out << " of ";
switch( card.suit() )
{
case Card::spades: out << "spades"; break;
case Card::clubs: out << "clubs"; break;
case Card::diamonds: out << "diamonds"; break;
case Card::hearts: out << "hearts"; break;
default: out << "unknown suit"; break;
}
return out;
} int main( ) {
const int num_players = 2;
vector< list<Card> > hands( num_players );
// deal first player a hand
hands[0].push_front( Card( 12, Card::hearts ) );
hands[0].push_front( Card( 1, Card::spades ) );
hands[0].push_front( Card( 4, Card::spades ) );
// deal second player a hand
hands[1].push_front( Card( 13, Card::diamonds ) );
hands[1].push_front( Card( 12, Card::clubs ) );
hands[1].push_front( Card( 2, Card::hearts ) );
const int num_plays = 3;
bool discard[num_players][num_plays] = { { true, true, false },
{ true, false, false } };
vector<Card> discard_pile;
// simulate card play
for( int i = 0; i < num_plays; ++i )
for( int j = 0; j < num_players; ++j )
// if discard and hand not empty...
if( discard[j][i] && !hands[j].empty() )
{
discard_pile.push_back( hands[j].front() );
hands[j].pop_front();
cout << "Player " << (j+1) << " discarded a "
<< discard_pile.back() << endl;
}// if pick up and discard pile not empty...
else if( !discard[j][i] && !discard_pile.empty() )
{
hands[j].push_back( discard_pile.back() );
cout << "Player " << (j+1) << " picked up a "
<< discard_pile.back() << endl;
discard_pile.pop_back();
}
}</source>
Demonstrating the STL vector back and pop_back operations
<source lang="cpp">#include <iostream>
- include <vector>
- include <string>
using namespace std; int main() {
string s("abcdefghij");
vector<char> vector1(s.begin(), s.end());
while (vector1.size() > 0) {
cout << vector1.back();
vector1.pop_back();
}
cout << endl;
return 0;
}</source>
jihgfedcba
Get the last element in the vector
<source lang="cpp">#include <iostream> using std::cout; using std::endl;
- include <vector> // vector class-template definition
- include <algorithm> // copy algorithm
- include <iterator> // ostream_iterator iterator
- include <stdexcept> // out_of_range exception
int main() {
int array[ 6 ] = { 1, 2, 3, 4, 5, 6 };
std::vector< int > integers( array, array + 6 );
std::ostream_iterator< int > output( cout, " " );
integers.push_back( 2 );
integers.push_back( 3 );
integers.push_back( 4 );
cout << "Vector integers contains: ";
std::copy( integers.begin(), integers.end(), output );
cout << "\nLast element of integers: " << integers.back();
return 0;
}</source>
Vector integers contains: 1 2 3 4 5 6 2 3 4 Last element of integers: 4
