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C++ Data Structures & STL

The Standard Template Library (STL) in C++ is a powerful set of C++ template classes to provide general-purpose classes and functions with templates. It includes data structures and algorithms that can be used to manage collections of data efficiently.

Key Topics

Overview of STL

STL provides a collection of algorithms and data structures that greatly simplifies the process of programming in C++. It is divided into four main components:

  • Containers
  • Iterators
  • Algorithms
  • Functors

Containers

Containers are objects that store data. STL provides several types of containers:

  • vector: Dynamic array that can resize itself.
  • list: Doubly linked list.
  • deque: Double-ended queue.
  • set: Collection of unique elements.
  • map: Collection of key-value pairs.

Example: Using a Vector

#include 
#include 
using namespace std;

int main() {
    vector numbers;
    numbers.push_back(10);
    numbers.push_back(20);
    numbers.push_back(30);
    cout << "Vector elements: ";
    for(int num : numbers) {
        cout << num << " ";
    }
    return 0;
}

Output:

Vector elements: 10 20 30

Iterators

Iterators are used to traverse the elements of a container. They provide a way to access the elements without exposing the underlying structure of the container.

Example: Using an Iterator with a Vector

#include 
#include 
using namespace std;

int main() {
    vector numbers = {10, 20, 30};
    cout << "Vector elements using iterator: ";
    for(auto it = numbers.begin(); it != numbers.end(); ++it) {
        cout << *it << " ";
    }
    return 0;
}

Output:

Vector elements using iterator: 10 20 30

Algorithms

STL provides a rich set of algorithms that can be used with containers. These algorithms include operations such as sorting, searching, and manipulating data.

Example: Using the Sort Algorithm

#include 
#include 
#include 
using namespace std;

int main() {
    vector numbers = {30, 10, 20};
    sort(numbers.begin(), numbers.end());
    cout << "Sorted elements: ";
    for(int num : numbers) {
        cout << num << " ";
    }
    return 0;
}

Output:

Sorted elements: 10 20 30

Custom Data Structures

In addition to the built-in containers provided by STL, you can also create your own custom data structures using classes. This allows for more complex data management and functionality.

Example: Custom Linked List

#include 
using namespace std;

class Node {
public:
    int data;
    Node* next;
    Node(int val) : data(val), next(nullptr) {}
};

class LinkedList {
public:
    Node* head;
    LinkedList() : head(nullptr) {}
    void append(int val) {
        Node* newNode = new Node(val);
        if (!head) {
            head = newNode;
        } else {
            Node* temp = head;
            while (temp->next) {
                temp = temp->next;
            }
            temp->next = newNode;
        }
    }
    void display() {
        Node* temp = head;
        while (temp) {
            cout << temp->data << " ";
            temp = temp->next;
        }
    }
};

int main() {
    LinkedList list;
    list.append(10);
    list.append(20);
    list.append(30);
    cout << "Linked List elements: ";
    list.display();
    return 0;
}

Output:

Linked List elements: 10 20 30

Key Takeaways

  • STL provides a powerful set of data structures and algorithms for efficient programming in C++.
  • Understand the different types of containers available in STL: vector, list, set, and map.
  • Utilize iterators to traverse and manipulate data within containers.
  • Leverage built-in algorithms like sorting and searching to simplify your code.
  • Create custom data structures using classes for more complex data management.
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