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2010-05-25T14:21:17Z

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

<source lang="cpp">#include <iostream>
#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 elements in int array to vector==

<source lang="cpp">#include <iostream>
#include <vector>
#include <cassert>
#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;
}</source>
<pre class=codeResult>28</pre>

==Assign value to the last element==

<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.
*/
#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <iterator>
using namespace std;
int main()
{
// create empty vector for strings
vector<string> sentence;
// reserve memory for five elements to avoid reallocation
sentence.reserve(5);
// append some elements
sentence.push_back("Hello,");
sentence.push_back("how");
sentence.push_back("are");
sentence.push_back("you");
sentence.push_back("?");
// assign "!" to the last element
sentence.back() = "!";
// print elements separated with spaces
copy (sentence.begin(), sentence.end(),
ostream_iterator<string>(cout," "));
cout << endl;
}</source>
<pre class=codeResult>Hello, how are you !</pre>

==Computing an inner product of tuples represented as vectors==

<source lang="cpp">#include <vector>
#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;
}</source>
<pre class=codeResult>4000</pre>

==creates a vector of 10 ints with value 100==

<source lang="cpp">#include <vector>
using namespace std;
int main(int argc, char** argv)
{
vector<int> intVector(10, 100); // creates a vector of 10 ints with value 100
return (0);
}</source>

==creates a vector of ints with zero elements==

<source lang="cpp">#include <vector>
using namespace std;
int main(int argc, char** argv)
{
vector<int> intVector; // creates a vector of ints with zero elements
return (0);
}</source>

==Demonstrating STL vector constructors with a user-defined type==

<source lang="cpp">#include <iostream>
#include <cassert>
#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">#include <iostream>
#include <cassert>
#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;
}</source>
<pre class=codeResult>vector2[0].generation: 1
vector2[1].generation: 1
vector2[2].generation: 1
Total copies: 3</pre>

==Demonstrating STL vector copying constructors==

<source lang="cpp">#include <iostream>
#include <cassert>
#include <vector>
using namespace std;
int main()
{
char name[] = "abcedfghijklmn";
vector<char> George(name, name + 6);
vector<char> son1(George); // Uses copy constructor
assert (son1 == George);
return 0;
}</source>

==Demonstrating the simplest STL vector constructors: duplicate chars==

<source lang="cpp">#include <iostream>
#include <cassert>
#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">#include <iostream>
#include <cassert>
#include <vector>
using namespace std;
int main()
{
vector<char> vector1;
cout << vector1.size();
return 0;
}</source>
<pre class=codeResult>0</pre>

==get an iterator that points to the maximum with max_element==

<source lang="cpp">#include <algorithm>
#include <iostream>
#include <vector>
using namespace std;
int main( )
{
vector<int> v( 10, 66 );
v[1] = 100;
// get an iterator that points to the maximum
vector<int>::iterator before_itr = max_element( v.begin(), v.end() );
cout << "The maximum before resizing is " << *before_itr;
}</source>

==Instantiate one vector and initialize it to the contents of another==

<source lang="cpp">#include <vector>
int main ()
{
std::vector <int> v;
// Instantiate a vector with 10 elements (it can grow larger)
std::vector <int> v1 (10);
// Instantiate a vector with 10 elements, each initialized to 90
std::vector <int> v2 (10, 90);
// Instantiate one vector and initialize it to the contents of another
std::vector <int> v3 (v2);
return 0;
}</source>

==Pass vector to a function==

<source lang="cpp">#include <iostream>
using std::cout;
using std::endl;
#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 << " ";
}</source>
<pre class=codeResult>2 3 4</pre>

==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.
*/
#include <iostream>
#include <string>
#include <algorithm>
#include <iterator>
#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 elements
sort (coll.begin(), coll.end());
// print all elements ignoring subsequent duplicates
unique_copy (coll.begin(), coll.end(),
ostream_iterator<string>(cout, "\n"));
}</source>
<pre class=codeResult>Terminate batch job (Y/N)? n</pre>

==The Instantiation of vector<bool>==

<source lang="cpp">#include <vector>
int main ()
{
using namespace std;
// Instantiate an object using the default constructor
vector <bool> vecBool1;
// A vector of 10 elements with value true (default: false)
vector <bool> vecBool2 (10, true);
// Instantiate one object as a copy of another
vector <bool> vecBool2Copy (vecBool2);
return 0;
}</source>

==Use generic vector to create vector of chars==

<source lang="cpp">#include <iostream>
#include <cassert>
#include <vector>
#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;
}</source>
<pre class=codeResult>b</pre>

==Use generic vector to create vector of integers==

<source lang="cpp">#include <iostream>
#include <cassert>
#include <vector>
#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;
}</source>
<pre class=codeResult>4</pre>

==Use generic vector to create vector of strings==

<source lang="cpp">// Demonstrating the generic find algorithm with a vector
#include <iostream>
#include <cassert>
#include <vector>
#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;
}</source>
<pre class=codeResult>1234</pre>

==Using the vector<bool>==

<source lang="cpp">#include <vector>
#include <iostream>
int main ()
{
using namespace std;
// Instantiate a vector<bool> to hold 3 elements
vector <bool> vecBool (3);
// Assign 3 elements using the array operator []
vecBool [0] = true;
vecBool [1] = true;
vecBool [2] = false;
// Insert a 4th element using push_back:
// this will cause the vector to resize the buffer
vecBool.push_back (true);
cout << "The contents of the vector are: " << endl << "{";
for (size_t nIndex = 0; nIndex < vecBool.size (); ++ nIndex)
cout << vecBool [nIndex] << " ";
cout << "}" << endl << endl;
vecBool.flip ();
cout << "The flipped contents of the vector are: " << endl << "{";
for (size_t nIndex = 0; nIndex < vecBool.size (); ++ nIndex)
cout << vecBool [nIndex] << " ";
cout << "}";
return 0;
}</source>

==Vector Init Array==

<source lang="cpp">#include <iostream>
#include <vector>
using namespace std;
void print( vector<int> );
int main()
{
int data[] = {11, 12, 23, 34};
int size = sizeof( data ) / sizeof( data[0] );
vector<int> vec( data, &data[ size ] );
print( vec ); // 11 12 23 34
return 0;
}
void print( vector<int> vec ) {
vector<int>::iterator p = vec.begin();
while ( p < vec.end() )
cout << *p++ << " ";
cout << endl;
}</source>

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