CodersPacket

The Standard Template Library (STL) is one of the most powerful tools in C++. It provides a collection of ready-to-use classes and functions for data structures and algorithms, making your code efficient and clean.

In this blog, we’ll explore the most used STL components: vector, map, set, and pair, with clear examples and outputs.

Introduction to STL in C++: Mastering Vectors, Maps, Sets, and Pairs

What is STL?

STL stands for Standard Template Library. It provides:

Containers: Like vector, map, set, etc.
Algorithms: Like sort(), find(), count(), etc.
Iterators: To traverse containers.

1. Vector in C++

A vector is a dynamic array that can grow and shrink during runtime.

#include <iostream>
#include <vector>
using namespace std;

int main() {
    vector<int> nums={10, 20, 30};
    nums.push_back(40);
    for(int i=0;i<nums.size();i++) {
        cout<<nums[i]<<" ";
    }
    return 0;
}

Output:
10 20 30 40

2. Map in C++

A map is a container that stores key-value pairs in sorted order by key.

#include <iostream>
#include <map>
using namespace std;

int main() {
    map<string,int>age;
    age["Alice"]=25;
    age["Bob"]=30;

    for(auto it:age) {
        cout<<it.first<<": "<<it.second<<endl;
    }
    return 0;
}

Output:
Alice: 25 
Bob: 30

3. Set in C++

A set stores unique elements in sorted order. Duplicates are automatically removed.

#include <iostream>
#include <set>
using namespace std;

int main() {
    set<int> s;
    s.insert(10);
    s.insert(5);
    s.insert(10); // Duplicate won't be added

    for(auto val:s){
        cout<<val<< " ";
    }
    return 0;
}

Output:
5 10

4. Pair in C++

A pair is a simple container to store two related values.

#include <iostream>
using namespace std;

int main() {
    pair<string,int> p;
    p=make_pair("CodeSpeedy", 2025);

    cout<<p.first<<" "<<p.second<<endl;
    return 0;
}

Output:
CodeSpeedy 2025