Purpose of the STL Vector
Vectors are STL (Standard Template Library) containers that support both direct and consecutive access to elements.
Vectors support all the features of the native C++ arrays but have some advantages. Vectors are implemented as dynamic arrays so they can change their size automatically.
The STL Vector is a template class so it supports multiple data types: all native C++ types and user defined types, structures and classes.
Tricks with Vectors
Add a New Element
- Add an element to the end of the vector
The method push_back is used to add an element to the end of the container.
#include <iostream>
#include <vector>
int main(int argc, char** argv)
{
std::vector<int> MyVector;
MyVector.push_back(1);
std::cout << MyVector[0] << std::endl;
return 0;
}
Add an element at certain position
The method insert should be used to extend the vector by adding a new element at a certain position
#include <iostream>
#include <vector>
int main(int argc, char** argv)
{
std::vector<int> MyVector;
//Add an element at the beginning with value 1
std::vector<int>::iterator Iter;
Iter = MyVector.begin();
MyVector.insert(Iter,1);
std::cout << MyVector[0] << std::endl;
return 0;
}
Delete an Element
- Delete an element at the end of the vector
The method pop_back should be used to remove an element at the end of the vector.
#include <iostream>
#include <vector>
int main(int argc, char** argv)
{
std::vector<int> MyVector;
MyVector.push_back(1);
MyVector.pop_back();
std::cout << MyVector.empty() << std::endl;
return 0;
}
The example add an element and after that deletes it. The execution of the application will result in 1 (true) because the vector will be empty.
Delete an element at a certain position
The method erase should be used to remove a certain element.
#include <iostream>
#include <vector>
int main(int argc, char** argv)
{
std::vector<int> MyVector;
MyVector.push_back(11);
MyVector.push_back(21);
std::vector<int>::iterator Iter;
//Delete the first element
Iter = MyVector.begin();
MyVector.erase( Iter );
//Show the first element (aka the second before calling erase)
Iter = MyVector.begin();
std::cout << *Iter << std::endl;
return 0;
}
Delete All Elements
To truncate the vector call clear.
#include <iostream>
#include <vector>
int main(int argc, char** argv)
{
std::vector<int> MyVector;
MyVector.push_back(11);
MyVector.push_back(21);
//Remove all elements
MyVector.clear();
std::cout << MyVector.empty() << std::endl;
return 0;
}
Access to Elements of a STL Vector
- Loop through Elements with an Iterator
#include <iostream>
#include <vector>
typedef std::vector<int> VectorInt;
typedef VectorInt::iterator VectorIntIter;
int main(int argc, char** argv)
{
VectorInt MyVector;
MyVector.push_back(11);
MyVector.push_back(21);
MyVector.push_back(31);
for(VectorIntIter Iter = MyVector.begin(); Iter < MyVector.end(); Iter++)
{
std::cout << *Iter << std::endl;
}
return 0;
}
Direct Element Access
#include <iostream>
#include <vector>
typedef std::vector<int> VectorInt;
int main(int argc, char** argv)
{
VectorInt MyVector;
MyVector.push_back(11);
MyVector.push_back(21);
MyVector.push_back(31);
int nSize = MyVector.size();
for(int nIter=0; nIter < nSize; nIter++)
{
std::cout << MyVector[nIter] << std::endl;
}
return 0;
}
Class Reference
C++ : Reference : STL Containers : vector
C++ Vectors
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