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Algorithms

Introduction

The Standard Template Library (STL) in C++ is a powerful library that provides several generic classes and functions, which allows developers to manipulate data in an efficient and easy manner. One of the key components of the STL is the Algorithms library. The STL Algorithms library is a collection of ready-to-use generic algorithms that can be used to perform a variety of operations on data structures like arrays, lists, and vectors.

In this article, we'll cover the basics of STL Algorithms and how to use them effectively. Let's get started!

Basics of STL Algorithms

STL Algorithms are divided into several categories based on their functionality:

  1. Sorting: These algorithms are used to sort data in a specific order. Examples include sort(), stable_sort(), partial_sort(), etc.
  2. Searching: These algorithms help in finding elements or a range of elements in a data structure. Examples include find(), binary_search(), lower_bound(), etc.
  3. Modifying sequence operations: These algorithms are used to modify the data in a data structure. Examples include copy(), move(), swap(), etc.
  4. Non-modifying sequence operations: These algorithms do not modify the data but perform operations like counting, finding, etc. Examples include count(), mismatch(), equal(), etc.

Using STL Algorithms

Before using any algorithm, you need to include the algorithms library in your code. You can do this with the following line of code:

#include <algorithm>

Let's take a look at some of the commonly used algorithms:

sort()​

The sort() function is used to sort all elements in a data structure. Here is how you can use it:

std::vector<int> v = {4, 2, 3, 1, 5};
std::sort(v.begin(), v.end());

In the above code, sort() sorts the vector v in ascending order.

find()​

The find() function is used to find a specific element in a data structure. Here is how you can use it:

std::vector<int> v = {4, 2, 3, 1, 5};
auto result = std::find(v.begin(), v.end(), 3);

if (result != v.end()) {
    std::cout << "Element found";
} else {
    std::cout << "Element not found";
}

In the above code, find() searches for the number 3 in the vector. If it is found, it returns an iterator pointing to the element, else it returns an iterator pointing to v.end().

count()​

The count() function is used to count the occurrences of a specific element in a data structure. Here is how you can use it:

std::vector<int> v = {1, 2, 3, 4, 1, 2, 1, 3, 1};
int cnt = std::count(v.begin(), v.end(), 1);
std::cout << "Number 1 appears " << cnt << " times\n";

In the above code, count() counts the occurrences of 1 in the vector.

Conclusion

The STL Algorithms library is a powerful tool that can help you manipulate data in an efficient and easy manner. The examples we've covered here are just the tip of the iceberg, there are many more STL algorithms to explore. Remember to always include the algorithms library before using any of its functions. Good luck with your C++ journey!