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C++ STL Tutorial
Hope you already understand the concept of C++ Template which we already have discussed in one of the chapters. The C++ STL (Standard Template Library) is a powerful set of C++ template classes to provides general-purpose templatized classes and functions that implement many popular and commonly used algorithms and data structures like vectors, lists, queues, and stacks.
At the core of the C++ Standard Template Library are following three well-structured components:
Component | Description |
Containers | Containers are used to manage collections of objects of a certain kind. There are several different types of containers like deque, list, vector, map etc. |
Algorithms | Algorithms act on containers. They provide the means by which you will perform initialization, sorting, searching, and transforming of the contents of containers. |
Iterators | Iterators are used to step through the elements of collections of objects. These collections may be containers or subsets of containers. |
We will discuss about all the three C++ STL components in next chapter while discussing C++ Standard Library. For now, keep in mind that all the three components have a rich set of pre-defined functions which help us in doing complicated tasks in very easy fashion.
Let us take the following program demonstrates the vector container (a C++ Standard Template) which is similar to an array with an exception that it automatically handles its own storage requirements in case it grows:
#include <iostream>
#include <vector>
using namespace std;
int main()
{
// create a vector to store int
vector<int> vec;
int i;
// display the original size of vec
cout << "vector size = " << vec.size() << endl;
// push 5 values into the vector
for(i = 0; i < 5; i++){
vec.push_back(i);
}
// display extended size of vec
cout << "extended vector size = " << vec.size() << endl;
// access 5 values from the vector
for(i = 0; i < 5; i++){
cout << "value of vec [" << i << "] = " << vec[i] << endl;
}
// use iterator to access the values
vector<int>::iterator v = vec.begin();
while( v != vec.end()) {
cout << "value of v = " << *v << endl;
v++;
}
return 0;
}
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When the above code is compiled and executed, it produces following result:
vector size = 0
extended vector size = 5
value of vec [0] = 0
value of vec [1] = 1
value of vec [2] = 2
value of vec [3] = 3
value of vec [4] = 4
value of v = 0
value of v = 1
value of v = 2
value of v = 3
value of v = 4
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Here are following points to be noted related to various functions we used in the above example:
The push_back( ) member function inserts value at the end of the vector, expanding its size as needed.
The size( ) function displays the size of the vector.
The function begin( ) returns an iterator to the start of the vector.
The function end( ) returns an iterator to the end of the vector.
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