What is stl – STL Tutorials and Interview Questions PDF | What is Standard Template Library? | Complete C++ STL Tutorial for Beginners

What is stl: Are you having perfect knowledge of the C++ Programming Language? If yes, then discussing the STL C++ concepts can be easy and simple to understand by beginners and experienced developers. Also, freshers who are appearing for software developer interviews related to various programming languages can go through STL Tutorials and Interview Questions guide. Here, BTech Geeks have shared entire concept-related interview questions along with some sub-topics of standard template library tutorials.

Readers & learners who are excited to explore more about STL Tutorials & Interview Questions can get into the further sections and start learning the most important topics of the standard template library(STL). Move ahead and know the definition of STL and its components. Firstly, take a look at the available links of Interview Questions on STL Tutorials and ace up your preparation.

Standard Template Library Interview Questions and Tutorials

In the below modules, you will find a complete list of tutorials and interview questions on STL C++ Programming. This list of STL Tutorials aid beginners to learn the basic to advanced topics of the standard template library C++ efficiently.

Vector Interview Questions and Tutorials

  • What’s std::vector and why should I use std::vector?
  • 5 Different ways to Initialize a vector
  • How to Iterate or Loop over a Vector?
  • How to Iterate over a Vector in Reverse Order ( Backward direction )
  • How does std::vector works internally ?
  • How to fill a vector with random numbers in C++
  • Importance of Constructors while using User Defined Objects with std::vector
  • How to use vector efficiently in C++?
  • std::vector and Iterator Invalidation
  • Remove all occurences of an element from vector in O(n) complexity
  • Be careful with hidden cost of std::vector for user defined objects
  • Add elements in vector using vector::push_back
  • How to Print all elements of a vector in C++
  • How to initialize two dimensional Vector in C++ – (Initializing 2D Vectors / Matrix)
  • How to print Two Dimensional (2D) Vector in C++ ?
  • C++: Convert Array to Vector (7 Ways)
  • C++: Convert vector to array (4 Ways)
  • C++: Convert Set to Vector
  • C++: Convert Vector to Set ( 5 Ways )
  • C++: Print a vector in reverse order (5 Ways)
  • Vector Interview Questions
  • Interview Questions On Stl In C++
  • Stl Interview Questions For Experienced
  • C++ Stl Interview Questions For Experienced

Deque Interview Questions and Tutorials

List Interview Questions and Tutorials

Set Interview Questions and Tutorials

Map Interview Questions and Tutorials

Unordered_map Interview Questions and Tutorials

Unordered_set Interview Questions and Tutorials

STL Algorithm Interview Questions and Tutorials

  • Using std::find & std::find_if with User Defined Classes
  • Iterating over a range of User Defined objects and calling member function using std::for_each
  • std::for_each Tutorial: Usage Details with Examples
  • Stl In C++
  • Questions On Stl In C++
  • Stl Interview Questions For Experienced Pdf
  • C++ Stl Interview Questions
  • Stl Interview Questions
  • C++ Stl Questions
  • C++ Stl Pdf
  • Stl Questions C++

What is STL?

STL stands for Standard Template Library which is a pack of C++ template classes that provides general-purpose classes and functions with templates that are used to execute programming data structures and functions/algorithms like doubly linked lists (list), paired arrays (map), expandable arrays (vector), large string storage, and manipulation (rope), etc.

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Components of Standard Template Library (STL)

Standard Template Library (STL) is mainly included in three components. They are as follows:

  1. Algorithms
  2. Containers
  3. Iterators

Now, we will see about all these three components of the STL C++ with a neat description that helps you understand very clearly.

Sr.No Component & Description
1 Containers: Containers are utilized to handle collections of objects of a certain kind. There are numerous types of containers such as deque, list, vector, map, etc.
2 Algorithms: Algorithms act on containers. They provide the means by which you will execute the initialization, sorting, searching, and transforming of the contents of containers.
3 Iterators: Iterators are applied to step through the elements of collections of objects. These collections may be containers or subsets of containers.

Architecture of STL

The following image shows the hierarchy of the standard template library(STL). Just take a look at it before you start learning each component of STL.

STL Architecture

C++: STL Containers

In STL, the library of containers accommodates containers that are utilized for building data structures such as Linked list, trees, arrays, etc.

Basically, these containers are general, they can maintain elements of any datatype. For instance, dynamic arrays of char, integer, float, and other types are created by Vector. 

Container Description Header file iterator
vector vector is a class that creates a dynamic array allowing insertions and deletions at the back. <vector> Random access
list The list is the sequence containers that allow the insertions and deletions from anywhere. <list> Bidirectional
deque deque is the double-ended queue that allows the insertion and deletion from both ends. <deque> Random access
set set is an associate container for storing unique sets. <set> Bidirectional
multiset A multiset is an associate container for storing non- unique sets. <set> Bidirectional
map The map is an associate container for storing unique key-value pairs, i.e. each key is associated with only one value(one-to-one mapping). <map> Bidirectional
multimap multimap is an associate container for storing key-value pairs, and each key can be associated with more than one value. <map> Bidirectional
stack It follows last in first out(LIFO). <stack> No iterator
queue It follows first in first out(FIFO). <queue> No iterator
Priority-queue The first element out is always the highest priority element. <queue> No iterator

STL Vector Example Program

#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++) {

// 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;

return 0;


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

Use and Application of STL

  • A common library that allows containers and algorithm are called it STL and stores and manipulate various types of data. So, it protects us from determining these data structures & algorithms from the scratch.
  • Due to the STL, presently we don’t need to determine our sort function every time we make a distinct program or determine the same function twice for the various data types, rather we can simply utilize the generic container and algorithms in STL.
  • Also, it helps in saving more time, code, and effort while programming, therefore STL is gradually utilized in competitive programming, and moreover, it is reliable and fast.

Practice these:

  1. What Is Stl?
  2. Can We Use Stl In Coding Interviews
  3. Is Stl Allowed In Interview
  4. From Which Stl We Can Insert/Remove Data From Anywhere?
  5. Cpp Interview Questions For Freshers
  6. Stl Practice Questions