C++ Complete Guide to Standard Template Library (STL)

C++ is a high-level language that is popular among developers when they need to build something memory-intensive due to the standard template library, something that must load faster than the rest of the app. Many people suggest that beginners learn C or C++ as their first coding language so that they can understand the concept of programming much better.

If you are like me, you might have also learned how to code a loop that will sort the dataset you have. Now, imagine doing that on a large scale a thousand times! It has to be a tedious job for all the developers. What if I told you that you don’t have to write the same code again and again? Well, you don’t have to write any code for sorting at all. 

Here is where the Standard Template Library comes into play to make your coding experience with C++ much better. Why not check out the Standard Template Library and why you must learn STL to become a better developer? 

What is Standard Template Library (STL)?

If you are somewhat familiar with different coding languages, you might have noticed a pattern. When someone says this programming language is faster than another, you will see that the faster the language is, the harder it gets. 

C++ is one of those hard languages that require a lot of stuff that you might not find in other languages at all. Even a short and simple code, such as printing “Hello World,” necessitates a large number of lines, which is not the case with simpler coding languages like Python or JavaScript. 

This ability to perform memory-intensive work has made C++ popular despite it being one of the hardest programming languages. The Standard Template Library, or STL, makes your C++ code a lot shorter and easier to do. 

In short, like many programming languages C++ also offers some pre-built functions, these functions are the Standard Template Library. These functions and containers have some common vectors or arithmetic operations that are very common in C++ programming.  

Things to Know Before STL

You know about the header files in C++ that you need to call before you want to put something in the code. The Standard Template Library is not one single thing that you can call by using just one header. The STL is divided into four major categories:

• Containers
• Iterators
• Algorithm, and 
• Function Objects

Let us find out what each type is contributing to the Standard Template Library. 

Containers

The name implies that the container is some sort of barrier that holds something. So, what do containers in C++ hold? Depending on the type of data you want to store, the most common types are vectors, lists, stacks, and so on. 

If you want to contain vectors within containers, you must name the header file vectors. If you want to add some integer data inside that vector, then you have to put them inside <> sign. Why not check out some of the data types and how you can use them in your codes? 

Vectors

Vectors may be taught in schools, or they may be mentioned when discussing illustrators, a software capable of creating vector images. Vector data is the most adaptable type of dataset because it is simple to resize and does not require any quality sacrifices. 

Before coding, you have to add the header file at the top of your code like this: 

#include<vector>Code language: C++ (cpp)

When you want to put some value inside that vector data, then you have to do this. 

vector < int > v = { 213, 1213, 546, 210 };Code language: C++ (cpp)

In the above example, you can see we have contained some integer data inside a vector container. All the containers are similar to what you call an array. A lot of built-in functions are here that you might have used in an array like appending, popping, inserting, finding a new value, sorting, etc.  

And you can use all the built-in functions by following the v.function() system. 

Some of the well-known functions are:

• push_back(value): To add data at the end of the array
• pop_back(): To remove the last element. 
• insert(index, value): It takes two parameters, one is the index where you want to put the value and another one is the value, that you want to put inside.
• size(): This is very obvious; you will get to know the size of the vector. 
• empty(): Sometimes you have to check whether a vector is empty or not, the empty() function is a great help in that case.
• front(): If you want to get the first value of your vector then front() is your guy.
• back(): Does the opposite job of the previous one.
• at(index): It finds the value of a specific position 
• erase(index): Should be obvious, you just let it know the index and it will remove data from that index.
• clear(): It clears the vector, and removes everything. 

Queue 

The structure is almost similar to that of vectors, but it follows the first in, first out method. meaning you will push data from the back and pop it from the front. 

The structure will be as follows: 

#include <queue>
queue<data_type> variable_name;Code language: C++ (cpp)

Queue functions are similar to vector functions, but it has fewer options. You can only use push(), pop(), size(), front(), and back(). 

Stack 

Instead of “first in, last out,” stack push and pop data from the same end. The structure of a typical stack looks like this. 

#include <stack>
stack<data_type> variable_name;Code language: C++ (cpp)

The available functions are also something that works in the final function because you can only remove or add to the stack in the final portion. Some important available functions for the stack are, push(), pop(), top(), size(), empty(), etc.

Set

If you are familiar with Python, then this should not be a problem for you at all. Set in STL works almost identically to Python set. Just look at the code example where you call a set and add values to it. 

set < int > s;
s.insert(20);
s.insert(30);
s.insert(40);
s.insert(50);
s.insert(60);
s.insert(60);
s.insert(60);
auto i = s.begin();
cout << * i << endl;
cout << s.size() << endl;
s.find(20) != s.end() ? cout << "found" << endl : cout << "Nothing" << endl;
s.erase(30);
for (auto i = s.begin(); i != s.end(); i++) {
 cout << * i << " ";
}Code language: C++ (cpp)

Algorithm 

There are some common algorithms that you have to use during your operations with C++. The best news is that STL is now available, complete with pre-built functionality in the <algorithm> header file.

Now, let us check out some of the algorithms that you might want to use. 

sort()

When I was first learning to program, our teacher taught us to sort using loops. Imagine spending this much time on a big project to figure out the logic of a loop. You don’t have to! Simply use sort(), and you’re done. Let’s look at an example. 

sort(arr, arr+5);
for (int i = 0; i < 5; i++) {
  cout << arr[i] << " ";
}Code language: C++ (cpp)

You should get 1 2 3 4 as the output

reverse()

This is the best part about a programming language: you can just look at a command and guess what it can do. You can almost follow the same example as sort() and replace the sort() with reverse(). The result is simple: your data will be reversed. 

min_element() and max_element() 

If you want to find out the minimum value, then use min_element(), and if you want to use the maximum value, then use max_element(). As you might know, a lot of built-in functions take some parameters, and in the case of these two, it is the start iterator and the end iterator.  

When you put the necessary value inside it, it will find out the maximum or minimum value. 

Iterators

So far, we have seen algorithms, containers, and various functions from both of these concepts. Now, what are iterators in STL? Remember how we talked about begin() and end() in previous sections? Both of them are iterators in STL. Iterators are mainly used to point at the memory addresses of different containers. 

Iterators are a blessing for memory-intensive application as it helps to remove complexity and make your code much faster.

Conclusion

C++ might look hard on the surface due to its complex syntax but it gets easier when you keep practicing different aspects of it. Just look at the different functions of Standard Template Library, you can just look at the name and can tell which one can do what. 

So, if you want to start your career as a C++ developer, the Standard Template Library will make your coding experience much better.