Accessing Elements in a Vector Using Array Semantics
#include <iostream>
#include <vector>
using namespace std;
int main ()
{
vector <int> v;
// Insert sample integers into the vector:
v.push_back (50);
v.push_back (1);
v.push_back (987);
v.push_back (1001);
unsigned int nElementIndex = 0;
while (nElementIndex < v.size ()){
cout << "Element at position " << nElementIndex;
cout << " is: " << v [nElementIndex] << endl;
++ nElementIndex;
}
return 0;
}Accessing Elements in a Vector Using Pointer Semantics (Iterators)
#include <iostream>
#include <vector>
int main ()
{
using namespace std;
vector <int> v;
v.push_back (50);
v.push_back (1);
v.push_back (987);
v.push_back (1001);
// Access objects in a vector using iterators:
vector<int>::iterator i = v.begin();
while (i != v.end ())
{
size_t nElementIndex = distance (v.begin (),
i);
cout << "Element at position ";
cout << nElementIndex << " is: " << *i << endl;
// move to the next element
++ i;
}
return 0;
}Access the elements of a vector through an iterator.
#include <iostream>
#include <vector>
#include <cctype>
using namespace std;
int main()
{
vector<char> v(10); // create a vector of length 10
vector<char>::iterator p; // create an iterator
int i;
// assign elements in vector a value
p = v.begin();
i = 0;
while(p != v.end()) {
*p = i + "a";
p++;
i++;
}
// display contents of vector
cout << "Original contents:\n";
p = v.begin();
while(p != v.end()) {
cout << *p << " ";
p++;
}
cout << "\n\n";
// change contents of vector
p = v.begin();
while(p != v.end()) {
*p = toupper(*p);
p++;
}
// display contents of vector
cout << "Modified Contents:\n";
p = v.begin();
while(p != v.end()) {
cout << *p << " ";
p++;
}
cout << endl;
return 0;
}Add all the elements from vector Two to the end of vector One
#include <vector>
#include <algorithm>
#include <iterator>
#include <iostream>
using namespace std;
void printVector(const vector<int>& v){
copy(v.begin(), v.end(), ostream_iterator<int>(cout, " "));
cout << endl;
}
int main(int argc, char** argv){
vector<int> v1, v2;
int i;
v1.push_back(1);
v1.push_back(2);
v1.push_back(3);
v1.push_back(5);
// Insert it in the correct place
v1.insert(v1.begin() + 3, 4);
// Add elements 6 through 10 to v2
for (i = 6; i <= 10; i++) {
v2.push_back(i);
}
printVector(v1);
printVector(v2);
// add all the elements from v2 to the end of v1
v1.insert(v1.end(), v2.begin(), v2.end());
printVector(v1);
return (0);
}Add elements to the end of vector with push_back
#include <iostream>
#include <vector>
using namespace std;
void show(const char *msg, vector<int> vect);
int main() {
// Declare a vector that has an initial capacity of 10.
vector<int> v(10);
for(unsigned i=0; i < v.size(); ++i) v[i] = i*i;
show("Contents of v: ", v);
// Add elements to the end of v.
v.push_back(100);
v.push_back(121);
return 0;
}
// Display the contents of a vector<int>.
void show(const char *msg, vector<int> vect) {
cout << msg;
for(unsigned i=0; i < vect.size(); ++i)
cout << vect[i] << " ";
cout << "\n";
}append one more element. This causes reallocation
#include <algorithm>
#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;
}
}
int main( )
{
vector<double> v( 5, 2.78 );
v[2] = 0.0;
// make the vector as large as possible without reallocating
v.resize( v.capacity(), 2.78 );
// find the smallest number
vector<double>::iterator before_itr = min_element( v.begin(), v.end() );
// append one more element. This causes reallocation
v.push_back( 2.78 );
}Change element with const iterator
#include <vector>
#include <iostream>
using namespace std;
vector<double> makevector(int size){
vector<double> result;
for (int i=1; i<=size; i++) {
result.push_back(double(i));
}
return result;
}
void print(const vector<double>& l)
{
cout << "Size of vector is: " << l.size() << endl;
vector<double>::const_iterator i;
for (i=l.begin(); i!=l.end(); i++)
{
cout << (*i) << " ";
}
cout << endl;
}
int main()
{
vector<double> vector1=makevector(5);
vector<double>::iterator bi;
vector<double>::reverse_iterator ri;
ri=vector1.rbegin(); // Set iterator
while (ri!=vector1.rend()) cout << (*ri++) << " ";
cout << endl << endl;
// Change element with const iterator
cout << "Change first element with const iterator" << endl;
vector<double>::const_iterator ci;
ci=vector1.end();
ci--;
cout << *ci << endl;
}Change element with pointer
#include <vector>
#include <iostream>
using namespace std;
vector<double> makevector(int size){
vector<double> result;
for (int i=1; i<=size; i++) {
result.push_back(double(i));
}
return result;
}
void print(const vector<double>& l)
{
cout << "Size of vector is: " << l.size() << endl;
vector<double>::const_iterator i;
for (i=l.begin(); i!=l.end(); i++)
{
cout << (*i) << " ";
}
cout << endl;
}
int main()
{
vector<double> vector1=makevector(5);
vector<double>::iterator bi;
vector<double>::reverse_iterator ri;
ri=vector1.rbegin(); // Set iterator
while (ri!=vector1.rend()) cout << (*ri++) << " ";
cout << endl << endl;
// Change element
cout << "Change first element with mutable iterator" << endl;
bi=vector1.begin();
*bi=double(99);
print(vector1);
}Constructing a Container That Has Identical Elements
#include <vector>
#include <iostream>
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;
}
}
int main( )
{
const int num_elements = 5;
const float value = 3.14f;
// construct a vector filled with copies of one value
vector<float> v( num_elements, value );
print( v);
}Constructing a Container That Has Specified Values
#include <list>
#include <vector>
#include <iostream>
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;
}
}
int main( )
{
const int num_elements = 4;
const double data[num_elements] = { 4.78, 6.97, 8.81, 9.02 };
list<double> l( data, data + num_elements );
const char* flavors[] = { "A", "B", "C" };
vector<string> v( flavors,
flavors + sizeof( flavors ) / sizeof( flavors[0] ) );
// display containers
print( l );
print( v );
}Elements Being Created, Assigned, and Destroyed
#include <iostream>
#include <vector>
using namespace std;
class Element
{
public:
Element();
Element( const Element& );
~Element();
Element& operator=( const Element& );
};
inline
Element::Element()
{ cout << "\nIn default constructor"; }
inline
Element::Element( const Element& )
{ cout << "\nIn copy constructor"; }
inline
Element::~Element()
{ cout << "\nIn destructor"; }
inline
Element& Element::operator=( const Element& )
{
cout << "\nIn assignment operator";
return *this;
}
int main( )
{
cout << "Constructing Vector With Three Elements";
vector<Element> d( 3 );
cout << "\n\nDeleting First Element";
d.erase( d.begin() );
cout << "\n\nDeleting All Elements";
d.clear();
}Instantiate a vector to 5 elements taken from another
#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> vecArrayWithTenInitializedElements (10, 90);
// Instantiate one vector and initialize it to the contents of another
std::vector <int> vecArrayCopy (vecArrayWithTenInitializedElements);
// Instantiate a vector to 5 elements taken from another
std::vector<int> vecSomeElementsCopied(v.begin(), v.begin () + 5);
return 0;
}Instantiate a vector with 10 elements, each initialized to 90
#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> vecArrayWithTenInitializedElements (10, 90);
return 0;
}Instantiate a vector with 10 elements (it can grow larger)
#include <vector>
int main ()
{
std::vector <int> v;
// Instantiate a vector with 10 elements (it can grow larger)
std::vector <int> v1 (10);
return 0;
}Instantiate a vector with 4 elements, each initialized to 90
#include <vector>
#include <iostream>
int main ()
{
using namespace std;
// Instantiate a vector with 4 elements, each initialized to 90
vector <int> v (4, 90);
vector <int>::iterator i;
for ( i = v.begin (); i != v.end (); ++ i ){
cout << *i << " ";
}
return 0;
}Set Element Values in a vector Using Array Semantics
#include <vector>
#include <iostream>
int main ()
{
std::vector <int> v (4);
// Copy integer values into individual element locations
v [0] = 50;
v [1] = 1;
v [2] = 987;
v [3] = 1001;
std::cout << "The vector contains ";
std::cout << v.size () << " Elements";
return 0;
}The first and last element in vector as pointed to by begin() and end() - 1
#include <iostream>
#include <vector>
using namespace std;
void show(const char *msg, vector<int> vect);
int main() {
// Declare a vector that has an initial capacity of 10.
vector<int> v(10);
for(unsigned i=0; i < v.size(); ++i) v[i] = i*i;
show("Contents of v: ", v);
// the use of the subscripting operator.
int sum = 0;
for(unsigned i=0; i < v.size(); ++i) sum += v[i];
double avg = sum / v.size();
cout << "The average of the elements is " << avg << "\n\n";
// Add elements to the end of v.
v.push_back(100);
v.push_back(121);
show("v after pushing elements onto the end: ", v);
cout << endl;
// Now use pop_back() to remove one element.
v.pop_back();
show("v after back-popping one element: ", v);
cout << endl;
cout << "The first and last element in v as"
<< " pointed to by begin() and end()-1:\n"
<< *v.begin() << ", " << *(v.end()-1) << "\n\n";
return 0;
}
void show(const char *msg, vector<int> vect) {
cout << msg << endl;
for(unsigned i=0; i < vect.size(); ++i)
cout << vect[i] << endl;
}The first and last element in vector as pointed to by rbegin() and rend() - 1
#include <iostream>
#include <vector>
using namespace std;
void show(const char *msg, vector<int> vect);
int main() {
// Declare a vector that has an initial capacity of 10.
vector<int> v(10);
for(unsigned i=0; i < v.size(); ++i) v[i] = i*i;
show("Contents of v: ", v);
// the use of the subscripting operator.
int sum = 0;
for(unsigned i=0; i < v.size(); ++i) sum += v[i];
double avg = sum / v.size();
cout << "The average of the elements is " << avg << "\n\n";
// Add elements to the end of v.
v.push_back(100);
v.push_back(121);
cout << "The first and last element in v as"
<< " pointed to by rbegin() and rend()-1:\n"
<< *v.rbegin() << ", " << *(v.rend()-1) << "\n\n";
return 0;
}
void show(const char *msg, vector<int> vect) {
cout << msg << endl;
for(unsigned i=0; i < vect.size(); ++i)
cout << vect[i] << endl;
}Vector Creation and Element Access
#include <iostream>
#include <string>
#include <vector>
using namespace std;
class Employee
{
public:
Employee();
Employee(const string& name, const int age);
Employee(const Employee& rhs);
~Employee();
void SetName(const string& name);
string GetName() const;
void SetAge(const int age);
int GetAge() const;
Employee& operator=(const Employee& rhs);
private:
string itsName;
int itsAge;
};
Employee::Employee()
: itsName("New Employee"), itsAge(16)
{}
Employee::Employee(const string& name, const int age)
: itsName(name), itsAge(age)
{}
Employee::Employee(const Employee& rhs)
: itsName(rhs.GetName()), itsAge(rhs.GetAge())
{}
Employee::~Employee()
{}
void Employee::SetName(const string& name)
{
itsName = name;
}
string Employee::GetName() const
{
return itsName;
}
void Employee::SetAge(const int age)
{
itsAge = age;
}
int Employee::GetAge() const
{
return itsAge;
}
Employee& Employee::operator=(const Employee& rhs)
{
itsName = rhs.GetName();
itsAge = rhs.GetAge();
return *this;
}
ostream& operator<<(ostream& os, const Employee& rhs)
{
os << rhs.GetName() << " is " << rhs.GetAge() << " years old";
return os;
}
template<class T>
void ShowVector(const vector<T>& v); // display vector properties
typedef vector<Employee> SchoolClass;
int main()
{
Employee Harry;
Employee Sally("Sally", 15);
Employee Bill("Bill", 17);
Employee Peter("Peter", 16);
SchoolClass EmptyClass;
cout << "EmptyClass:\n";
ShowVector(EmptyClass);
SchoolClass GrowingClass(3);
cout << "GrowingClass(3):\n";
ShowVector(GrowingClass);
GrowingClass[0] = Harry;
GrowingClass[1] = Sally;
GrowingClass[2] = Bill;
cout << "GrowingClass(3) after assigning students:\n";
ShowVector(GrowingClass);
GrowingClass.push_back(Peter);
cout << "GrowingClass() after added 4th student:\n";
ShowVector(GrowingClass);
GrowingClass[0].SetName("Harry");
GrowingClass[0].SetAge(18);
cout << "GrowingClass() after Set\n:";
ShowVector(GrowingClass);
return 0;
}
template<class T>
void ShowVector(const vector<T>& v)
{
cout << "max_size() = " << v.max_size();
cout << "\tsize() = " << v.size();
cout << "\tcapacity() = " << v.capacity();
cout << "\t" << (v.empty()? "empty": "not empty");
cout << "\n";
for (int i = 0; i < v.size(); ++i)
cout << v[i] << "\n";
cout << endl;
}
