в 14:21, 25 мая 2010

2010-05-25T14:21:06Z

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2010-05-25T10:27:41Z

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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 Items 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;
}
/*
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.
*/
#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 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">

#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;
}
/*
4000
*/

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

</source>

==Demonstrating STL vector copying constructors==

<source lang="cpp">

#include <iostream>
#include <cassert>
#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">

#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;
}
/*
0
*/

</source>

==Pass vector of integer to a function==

<source lang="cpp">
#include <iostream>
#include <numeric>
#include <vector>
#include <cmath>
#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">

#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 << " ";
}
/*
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.
*/
#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 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">
#include <iostream>
#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">

#include <iostream>
#include <vector>
#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">

#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;
}
/*
b
*/

</source>

==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;
}
/*
4
*/

</source>

==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;
}
/*
1234
*/

</source>

==Use typedef to define new type based on vector==

<source lang="cpp">
#include <algorithm>
#include <vector>
#include <string>
#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>

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