C++/Vector/vector

Add class to a vector and then delete them one by one

<source lang="cpp">

1. include <iostream>
2. include <vector>

using namespace std; class MyClass { }; int main( ) {

  vector<MyClass*> vec;
  MyClass* p = NULL;
  for (int i = 0; i < 10; i++) {
     p = new MyClass( );
     vec.push_back(p);
  }
  for (vector<MyClass*>::iterator pObj = vec.begin( );
       pObj != vec.end( ); ++pObj) {
     delete *pObj;
  }
  vec.clear( );

}

 </source>

Assign Items in int array to vector

<source lang="cpp">

1. include <iostream>
2. include <vector>
3. include <cassert>
4. include <numeric> // for accumulate

using namespace std; int main() {

 int x[5] = {2, 3, 5, 7, 11};
 vector<int> vector1(&x[0], &x[5]);
 int sum = accumulate(vector1.begin(), vector1.end(), 0);
 cout << sum << endl;
 return 0;

} /* 28

*/        
   
   
 </source>

Assign value to the last Item

<source lang="cpp">

/* The following code example is taken from the book

* "The C++ Standard Library - A Tutorial and Reference"
* by Nicolai M. Josuttis, Addison-Wesley, 1999
*
* (C) Copyright Nicolai M. Josuttis 1999.
* Permission to copy, use, modify, sell and distribute this software
* is granted provided this copyright notice appears in all copies.
* This software is provided "as is" without express or implied
* warranty, and with no claim as to its suitability for any purpose.
*/

1. include <iostream>
2. include <vector>
3. include <string>
4. include <algorithm>
5. include <iterator>

using namespace std; int main() {

   // create empty vector for strings
   vector<string> sentence;
   // reserve memory for five Items to avoid reallocation
   sentence.reserve(5);
   // append some Items
   sentence.push_back("Hello,");
   sentence.push_back("how");
   sentence.push_back("are");
   sentence.push_back("you");
   sentence.push_back("?");
   // assign "!" to the last Item
   sentence.back() = "!";
   // print Items separated with spaces
   copy (sentence.begin(), sentence.end(),
         ostream_iterator<string>(cout," "));
   cout << endl;

} /* Hello, how are you !

*/        
   
   
 </source>

Computing an inner product of tuples represented as vectors

<source lang="cpp">

1. include <vector>
2. include <iostream>

using namespace std; int main() {

 const long N = 600000; // Length of tuples x and y
 const long S = 10;     // Sparseness factor
 vector<double> x(N), y(N);

 for (long k = 0; 3 * k * S < N; ++k)
   x[3 * k * S] = 1.0;
 for (long k = 0; 5 * k * S < N; ++k)
   y[5 * k * S] = 1.0;
 double sum = 0.0;
 for (long k = 0; k < N; ++k)
   sum += x[k] * y[k];
 cout << sum << endl;
 return 0;

} /* 4000

*/        
   
   
 </source>

Demonstrating STL vector constructors with a user-defined type

<source lang="cpp">

1. include <iostream>
2. include <cassert>
3. include <vector>

using namespace std; class MyClass { public:

 unsigned long id;
 MyClass() : id(0) { }
 MyClass(unsigned long x) : id(x) { }

}; bool operator==(const MyClass& x, const MyClass& y) {

 return x.id == y.id;

} bool operator!=(const MyClass& x, const MyClass& y) {

 return x.id != y.id;

}

int main() {

 vector<MyClass> vector1, vector2(3);
 assert (vector1.size() == 0);
 assert (vector2.size() == 3);
 assert (vector2[0] == MyClass() && vector2[1] == MyClass() &&vector2[2] == MyClass());
 assert (vector2 == vector<MyClass>(3, MyClass()));
 return 0;

}

 </source>

Demonstrating STL vector constructors with a user-defined type and showing copying explicitly

<source lang="cpp">

1. include <iostream>
2. include <cassert>
3. include <vector>

using namespace std; class MyClass { public:

 unsigned long id;
 unsigned long generation;
 static unsigned long total_copies;
 MyClass() : id(0), generation(0) { }
 MyClass(unsigned long n) : id(n), generation(0) { }
 MyClass(const MyClass& z) : id(z.id), generation(z.generation + 1) {
   ++total_copies;
 }

}; bool operator==(const MyClass& x, const MyClass& y) {

 return x.id == y.id;

} bool operator!=(const MyClass& x, const MyClass& y) {

 return x.id != y.id;

} unsigned long MyClass::total_copies = 0; int main() {

 vector<MyClass> vector1, vector2(3);
 assert (vector1.size() == 0);
 assert (vector2.size() == 3);
 assert (vector2[0] == MyClass() && vector2[1] == MyClass() &&
         vector2[2] == MyClass());
 for (int i = 0; i != 3; ++i)
   cout << "vector2[" << i << "].generation: " << vector2[i].generation << endl;
 cout << "Total copies: " << MyClass::total_copies << endl;
 return 0;

} /* vector2[0].generation: 1 vector2[1].generation: 1 vector2[2].generation: 1 Total copies: 3

*/        
   
   
 </source>

Demonstrating STL vector copying constructors

<source lang="cpp">

1. include <iostream>
2. include <cassert>
3. include <vector>

using namespace std; int main() {

 char name[] = "abcedfghijklmn";
 vector<char> myVector(name, name + 6);
 vector<char> myVector2(myVector); // Uses copy constructor
 assert (myVector2 == myVector);
 return 0;

}

 </source>

Demonstrating the simplest STL vector constructors: duplicate chars

<source lang="cpp">

1. include <iostream>
2. include <cassert>
3. include <vector>

using namespace std; int main() {

 vector<char> vector2(3, "x");
 assert (vector2.size() == 3);
 assert (vector2[0] == "x" && vector2[1] == "x" && vector2[2] == "x");
 assert (vector2 == vector<char>(3, "x"));
 return 0;

}

 </source>

Demonstrating the simplest STL vector constructors: empty vector

<source lang="cpp">

1. include <iostream>
2. include <cassert>
3. include <vector>

using namespace std; int main() {

 vector<char> vector1;
 cout << vector1.size();
 return 0;

} /* 0

*/        
   
   
 </source>

Pass vector of integer to a function

<source lang="cpp">

1. include <iostream>
2. include <numeric>
3. include <vector>
4. include <cmath>
5. include <functional>

using namespace std; double geometricMean(const vector<int>& nums) {

 double mult = accumulate(nums.begin(), nums.end(), 1,multiplies<int>());
 return (pow(mult, 1.0 / nums.size()));

}

int main(int argc, char** argv) {

 plus<int> myPlus;
 int res = myPlus(4, 5);
 cout << res << endl;
 vector<int> myVector;
 int num;
 while (true) {
   cout << "Enter a test score to add (0 to stop): ";
   cin >> num;
   if (num == 0) {
     break;
   }
   myVector.push_back(num);
 }
 cout << "The geometric mean is " << geometricMean(myVector) << endl;
 return (0);

}

 </source>

Pass vector to a function

<source lang="cpp">

1. include <iostream>

using std::cout; using std::endl;

1. include <vector>

using std::vector; template < typename T > void printVector( const vector< T > &integers2 ); int main() {

  int array[ 6 ] = { 1, 2, 3, 4, 5, 6 }; // initialize array
  vector< int > integers; // create vector of ints
  integers.push_back( 2 );
  integers.push_back( 3 );
  integers.push_back( 4 );
  printVector( integers );
  cout << endl;
  return 0;

} template < typename T > void printVector( const vector< T > &integers2 ){

  typename vector< T >::const_iterator constIterator;
  for ( constIterator = integers2.begin();
     constIterator != integers2.end(); ++constIterator )
     cout << *constIterator << " ";

} /* 2 3 4

*/        
   
   
 </source>

Read keyboard input to a vector

<source lang="cpp">

/* The following code example is taken from the book

* "The C++ Standard Library - A Tutorial and Reference"
* by Nicolai M. Josuttis, Addison-Wesley, 1999
*
* (C) Copyright Nicolai M. Josuttis 1999.
* Permission to copy, use, modify, sell and distribute this software
* is granted provided this copyright notice appears in all copies.
* This software is provided "as is" without express or implied
* warranty, and with no claim as to its suitability for any purpose.
*/

1. include <iostream>
2. include <string>
3. include <algorithm>
4. include <iterator>
5. include <vector>

using namespace std; int main() {

   /* create a string vector
    * - initialized by all words from standard input
    */
   vector<string> coll((istream_iterator<string>(cin)),
                       istream_iterator<string>());
   // sort Items
   sort (coll.begin(), coll.end());
   // print all Items ignoring subsequent duplicates
   unique_copy (coll.begin(), coll.end(),
                ostream_iterator<string>(cout, "\n"));

} /* Terminate batch job (Y/N)? n

*/        
   
   
 </source>

Requirements for Classes Used in Vectors

<source lang="cpp">

1. include <iostream>
2. include <vector>

using namespace std; template <class T> void print(T& c){

  for( typename T::iterator i = c.begin(); i != c.end(); i++ ){
     std::cout << *i << endl;
  }

} class Item {

  public:
  Item();
  ~Item();
  Item( const Item& );
  Item& operator=( const Item& );
  private:
  static int default_constructor_calls_;
  static int assignment_calls_;
  static int copy_constructor_calls_;
  static int destructor_calls_;

}; inline Item::Item() { cout << "\nCall " << ++default_constructor_calls_

    << " of default constructor";

} inline Item::Item( const Item& ) {

  cout << "\nCall " << ++copy_constructor_calls_
     << " of copy constructor";

} inline Item::~Item() { cout << "\nCall " << ++destructor_calls_ << " of destructor"; } inline Item& Item::operator=( const Item& ) {

  cout << "\nCall " << ++assignment_calls_
     << " of assignment operator";
  return *this;

} int Item::default_constructor_calls_ = 0; int Item::assignment_calls_ = 0; int Item::copy_constructor_calls_ = 0; int Item::destructor_calls_ = 0; int main( ) {

  vector<Item> d( 2 );

  d.resize( d.capacity() );
  d.push_back( Item() );
  d.erase( d.begin() );

}

 </source>

Store a class object in a vector

<source lang="cpp">

1. include <iostream>
2. include <vector>
3. include <cstdlib>

using namespace std; class MyClass {

 int value;

public:

 MyClass() { value = 0; }
 MyClass(int x) { value = x; }
 MyClass &operator=(int x) {
   value = x; return *this;
 }
 double get_value() { return value; }

}; bool operator<(MyClass a, MyClass b) {

 return a.get_value() < b.get_value();

} bool operator==(MyClass a, MyClass b) {

 return a.get_value() == b.get_value();

} int main() {

 vector<MyClass> v;
 for(int i=0; i<7; i++)
   v.push_back(MyClass(60 + rand()0));
 cout << "Farenheit valueeratures:\n";
 for(int i=0; i<v.size(); i++)
   cout << v[i].get_value() << " ";
 cout << endl;
 for(int i=0; i<v.size(); i++)
   v[i] = (int) (v[i].get_value()-32) * 5/9 ;
 cout << "Centigrade valueeratures:\n";
 for(int i=0; i<v.size(); i++)
   cout << v[i].get_value() << " ";
 return 0;

} /* Farenheit valueeratures: 71 77 64 70 89 64 78 Centigrade valueeratures: 21 25 17 21 31 17 25

*/        
   
   
 </source>

Use generic vector to create vector of chars

<source lang="cpp">

1. include <iostream>
2. include <cassert>
3. include <vector>
4. include <algorithm> // For find

using namespace std;

int main() {

 char x[5] = {"a", "b", "c", "d", "f"};
 vector<char> vector1(&x[0], &x[5]);
 // Search for the first occurrence
 vector<char>::iterator where = find(vector1.begin(), vector1.end(), "b");

 cout << *where  << endl;
 return 0;

} /* b

*/        
   
   
 </source>

Use generic vector to create vector of integers

<source lang="cpp">

1. include <iostream>
2. include <cassert>
3. include <vector>
4. include <algorithm> // For find

using namespace std;

int main() {

 int x[5] = {2, 4, 6, 8, 10};
 vector<int> vector1(&x[0], &x[5]);
 // Search for the first occurrence
 vector<int>::iterator where = find(vector1.begin(), vector1.end(), 4);

 cout << *where  << endl;
 return 0;

} /* 4

*/        
   
   
 </source>

Use generic vector to create vector of strings

<source lang="cpp">

// Demonstrating the generic find algorithm with a vector

1. include <iostream>
2. include <cassert>
3. include <vector>
4. include <algorithm> // For find

using namespace std;

int main() {

 string x[5] = {"1234", "2345", "3456", "4567", "0987"};
 vector<string> vector1(&x[0], &x[5]);
 // Search for the first occurrence
 vector<string>::iterator where = find(vector1.begin(), vector1.end(), "1234");

 cout << *where  << endl;
 return 0;

} /* 1234

*/        
   
   
 </source>

Use typedef to define new type based on vector

<source lang="cpp">

1. include <algorithm>
2. include <vector>
3. include <string>
4. include <iostream>

using namespace std; typedef vector <string> VECTOR_STRINGS; int main () {

   VECTOR_STRINGS v;
   v.push_back ("A");
   v.push_back ("B");
   v.push_back ("C");
   v.push_back ("D");
   // insert a duplicate into the vector
   v.push_back ("D");
   for (size_t nItem = 0; nItem < v.size (); ++ nItem){
       cout << "Name [" << nItem << "] = \"";
       cout << v [nItem] << "\"" << endl;
   }
   return 0;

}

 </source>