Standard Template Library (STL) in C++.

1. Standard Template Library (STL)
In C++
Mandeep Singh
Asst. Prof.
HMRITM (GGSIPU)

2. Standard Template Library
The C++ STL (Standard Template Library) is a
powerful set of C++ template classes to
provide general-purpose classes and
functions.
With templates that implement many popular
and commonly used algorithms and data
structures like lists, queues, and stacks.

3. C++ Standard Template Library are following three well-
structured components −
Sr. No Component & Description
1 Containers: (Organizing stored data in memory)
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.
2 Algorithms: (Procedures applied to process their data)
Algorithms act on containers. They provide the means by which you will
perform initialization, sorting, searching, and transforming of the
contents of containers.
3 Iterators: (Point to the elements in a container)
Iterators are used to step through the elements of collections of
objects. These collections may be containers or subsets of containers.

4. STL Containers
1) Sequence container: vector, deque, list
2) Associative container: map, multimap, set , multiset,
3) Un-ordered associative container: unordered-map,
unordered-multimap, unordered-set, unordered-multiset
4) Container adapter: queue, priority queue, stack

5. Sequence container
-It is used to implement data structure which can
be accessed in a sequential manner.
Vector- It is same as dynamic arrays offer random
access back insertion.
Eg: int array[5]= {12,7,9,21,13};
Vector <int> v(array, array +5);
12,7,9,21,13 // V[3]=21
Functions of vector:- Push(), Pop().
V. Push_back(15); V.Pop_back(15);
12 7 9 21 13 15 12 7 9 21 13

6. //Program to demonstrate the vector container
#include<iostream>
#include<vector>
Using namespace std;
Int main()
{
Vector <int> V;
V. Push_back(1); //insert 1 at the back of V
V. Push_back(2); //insert 2 at the back of V
V. Push_back(4); //insert 4 at the back of V
For (Vector<int>:: iterator i=V, begin (1);
i!= V. End(); i++)
{
Cout <<*i <<””; // for printing the vector particular address location
}
}
O/P: 1 2 4

7. Vector Container Continue…
 Program that demonstrates the vector
container which is similar to an array with an
exception that it automatically handles its
own storage requirements in case it grows.

8. //Program to demonstrates the vector container:
#include <iostream>
#include <vector>
using namespace std;
int main() {
int vector<int> vec; // create a vector to store
int i;
cout << "vector size = " << vec.size() << endl; // display the original size of vec
for(i = 0; i < 5; i++) // push 5 values into the vector
{vec.push_back(i); }
cout << "extended vector size = " << vec.size() ; // display extended size of vec
for(i = 0; i < 5; i++) { // access 5 values from the vector
cout << "value of vec [" << i << "] = " << vec[i] << endl; }
vector<int>::iterator v = vec.begin(); // use iterator to access the values
while( v != vec.end()) {
cout << "value of v = " << *v << endl;
v++; }
return 0; }

9. Associative and unordered associative containers
• Associative containers:
-used to implement stored data structure
Eg. Map, multimap, set, multiset
Eg. (1) map: maps are used to replicate associative arrays. It
contains stored key values pair, in which each key is unique,
and cannot be changed , it can insert and delete but cannot
alter.
O[n] -time complexity
Syntax: Map <key-type, value- type> map-name;
keys values
125 xyz

10. //Creating a map in different ways
#include<iostream>
#include<map>
Using namespace std;
int main ()
{
Map <int, int> m{[1,2],[2,3],[3,4]};
// creates a map in with keys 1,2,3 and their corresponding values 2,3,4
Map < string , int> map1;
// creates a map with keys of type char & Value of type integer
Map1 [“abc”]=100; // insert key=”abc” with value =100
Map1 [“b”]=200; // insert key=”b” with value=200
Map1 [“c”]=300; // insert key =”c” with value =300
Map1 [“def”]=400; // insert key=”def” with value=400
Map <char, int> map2 (map1. Begin(),Map1. End()); //creates a map map2
which have entries copied from map1. Begin() to map1. End()
}

11. Container adapter:
-It is used to provide different interface to the
sequence container
Eg. Queue , priority queue, stack
Queue: queue container is used to replicate queue in
c++, insertion always back, deletion always front of
queue
Syntax: queue <obj-type> queue-name;
Function: Push (), Pop(), size(), swap()
Eg. Back of queue front of queue2

12. //Program to demonstrate the Queue container
#include<iostream>
#include<queue>
Using namespace std;
int main()
{
queue <int> q; // creates an empty queue of int q
q. push(2); // Pushes 2 in the queue, now front=back=2
q. push(3); //Pushes 3 in the queue, now front=2, back=3
q.push(5);
}
O/P: 5 3 2

13. Priority queue
-It is just like a normal queue except the element
removed from the queue is always the
greatest among all the element in queue.
• Syntax: priority_queue <int> pq;
• Function: push(), Pop(), size(), swap()

14. //Program to demonstrate the Priority queue container
#include< iostream>
#include<queue>
Using namespace std;
int main()
{
priority_queue <int> pq;
Pq. Push (30); //insert 30 to pq now top=30
Pq. Push (40); // insert 40 to pq now top=40
Pq. Push (90); // insert 90 to pq now top =90
Pq. Push (60); // insert 60 to pq top stills 90
Pq. Pop () ; // removes 90
}

15. Stack:
Stack:
- insertion and deletion always performed at
top of the stack.
Syntax: stack<obj-type> stack_name;
Function: push (), pop(), top(), size(), swap()

16. //Program to demonstrate the Stack
#include<iostream>
#include <stack>
Using namespace std;
int main()
{
Stack <int> s; //create empty stack
S. push (2); //pushing element into stack
S. push(3);
S. push(4);
Cout << s.top(); //print 4
Cout << s. size(); //print 3
}

17. Thank You!!