🔴 Advanced · Lesson 58

Iterators in STL

What is Iterators in STL?

Iterators in STL
Iterators act like pointers to traverse STL containers. They provide a common way to move through vectors, sets, maps and other containers.

Level
🔴 STL, Modern C++ and Projects

Example File
iterators.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
iterator	Iterator used in Iterators in STL programming.
begin	Begin used in Iterators in STL programming.
end	End used in Iterators in STL programming.
dereference	Dereference used in Iterators in STL programming.
traversal	Traversal used in Iterators in STL programming.

Syntax / Pattern

for(auto it = v.begin(); it != v.end(); ++it)

Example Program

#include <iostream>
#include <vector>
using namespace std;
int main(){
    vector<int> v = {5,10,15};
    for(auto it = v.begin(); it != v.end(); ++it)
        cout << *it << " ";
}

Expected Output

5 10 15

Program Explanation

begin() points to first element.
end() points after last element.
*it gives current value.

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?

STL traversal
algorithms
generic programming

Common Mistakes

Dereferencing end() iterator.
Modifying container while using invalidated iterator.

Practice Tasks

Traverse map using iterator.
Explain begin() and end().

Summary

Iterators in STL 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.