🔴 Advanced · Lesson 57

set and map in STL

What is set and map in STL?

set and map in STL
set stores unique sorted values. map stores key-value pairs and is useful for fast lookup.

Level
🔴 STL, Modern C++ and Projects

Example File
set-map.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
set	Set used in set and map in STL programming.
map	Map used in set and map in STL programming.
key-value	Key-value used in set and map in STL programming.
unique	Unique used in set and map in STL programming.
lookup	Lookup used in set and map in STL programming.

Syntax / Pattern

map<Key,Value> m; m[key] = value;

Example Program

#include <iostream>
#include <map>
using namespace std;
int main(){
    map<string,int> marks;
    marks["Aman"] = 92;
    cout << marks["Aman"];
}

Expected Output

Program Explanation

Aman is the key.
92 is the value associated with the key.

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?

student marks
word frequency
configuration data

Common Mistakes

Using map when duplicate keys are required.
Forgetting that set stores unique values.

Practice Tasks

Count frequency of words using map.
Store unique roll numbers using set.

Summary

set and map 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.