Q14. Demonstrate Use of STL

Question:
Write program(s) to demonstrate use of Standard Template Library (STL).

My Approach

C++ ka STL (Standard Template Library) ek powerful library hai jisme ready-made classes aur functions diye gaye hote hain.
Isme mainly 4 parts hote hain:

1. Containers → Data ko hold karne ke liye (e.g. vector, list, map, set).
2. Iterators → Containers ko traverse karne ke liye.
3. Algorithms → Searching, sorting, reversing, etc.
4. Functors → Functions jinko objects ki tarah treat kiya ja sakta hai.

Real-life example:
Mujhe agar ek news website me latest headlines ko sorted order me dikhana ho, ya apne project Sortify me files ko alphabetically arrange karna ho, to STL ka use karna sabse fast aur easy hoga.

Program Code

File Name: stl_demo.cpp

#include <iostream>
#include <vector>
#include <algorithm>
#include <map>
using namespace std;
 
int main() {
    // 1. Vector Example
    vector<int> numbers = {5, 2, 8, 1, 9};
 
    cout << "Original Numbers: ";
    for (int n : numbers) cout << n << " ";
    cout << endl;
 
    // Sort the vector
    sort(numbers.begin(), numbers.end());
 
    cout << "Sorted Numbers: ";
    for (int n : numbers) cout << n << " ";
    cout << endl;
 
    // 2. Map Example
    map<int, string> students;
    students[101] = "Intesab";
    students[102] = "Rahul";
    students[103] = "Sumaira";
 
    cout << "\nStudent Records:" << endl;
    for (auto& pair : students) {
        cout << "Roll No: " << pair.first << " -> Name: " << pair.second << endl;
    }
 
    // 3. Algorithm Example
    int key = 8;
    if (binary_search(numbers.begin(), numbers.end(), key)) {
        cout << "\nElement " << key << " found in vector!" << endl;
    } else {
        cout << "\nElement " << key << " not found!" << endl;
    }
 
    return 0;
}

Output

Before Sorting:

Original Numbers: 5 2 8 1 9

After Sorting:

Sorted Numbers: 1 2 5 8 9

Student Records using Map:

Roll No: 101 -> Name: Intesab
Roll No: 102 -> Name: Rahul
Roll No: 103 -> Name: Sumaira

Search Example:

Element 8 found in vector!

Explanation

1. Vector

   • Dynamic array, jisme size automatically adjust hota hai.
   • Yaha sort() algorithm se vector ko sort kiya.

2. Map

   • Key-value pairs store karta hai.
   • Real life me roll no → student name mapping.

3. Algorithms

   • sort(), binary_search() jaise ready-made tools hote hain.
   • Fast, efficient aur reusable code.

Real-Life Scenario

• E-commerce website me products ko sort karne ke liye sort().
• Cybersecurity logs ko filter karne ke liye map ya set.
• Talkum (chat app) me users ke messages ko map ke form me store karna (user_id → message).

Conclusion

STL se C++ programming fast aur efficient hoti hai.
Yeh library har tarah ke data structures aur algorithms provide karti hai jisse code likhne ka time kam ho jata hai.

Submitted by:
Intesab Ansari
MCA Student, NMU University
Portfolio: intesab.live