🔴 Advanced · Lesson 59

STL Algorithms

What is STL Algorithms?

STL Algorithms
STL algorithms perform common operations such as sorting, searching, counting and reversing on containers.

Level
🔴 STL, Modern C++ and Projects

Example File
algorithms.cpp

Main Focus
Concept + syntax + practical C++ program

Why should you learn this?

It helps you write correct and readable C++ programs.
It is used repeatedly in school practicals, projects and competitive programming.
It builds the base for advanced topics such as OOP, STL and data structures.

Important Terms

Term	Meaning / Use
sort	Sort used in STL Algorithms programming.
find	Find used in STL Algorithms programming.
count	Count used in STL Algorithms programming.
reverse	Reverse used in STL Algorithms programming.
binary_search	Binary_search used in STL Algorithms programming.

Syntax / Pattern

sort(v.begin(), v.end());

Example Program

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
int main(){
    vector<int> v = {4,2,9};
    reverse(v.begin(), v.end());
    for(int x:v) cout << x << " ";
}

Expected Output

9 2 4

Program Explanation

reverse() reverses the order of elements.
Range is given using begin() and end().

Exam Tip: In C++ practical answers, write the logic first, then the program, then expected output. For theory, always include one suitable example.

Where will you use it?

data processing
competitive programming
clean code

Common Mistakes

Forgetting <algorithm>.
Using binary_search without sorting first.

Practice Tasks

Sort names alphabetically.
Find whether value exists in vector.

Summary

STL Algorithms is an important C++ topic. Learn the definition, understand the syntax, run the example program and then solve the practice tasks to make the concept strong.