Sequence Containers

A sequence container is a type of container provided by the Standard Template Library (STL) that stores elements in a linear sequence.

It maintains the order of elements as they are inserted and allows efficient access to elements using indexes.

Sequence containers offer various operations for adding, removing, and modifying elements, making them versatile and widely used in C++ programming.

Table of Contents

Types of Sequence Containers in STL:

There are four main types of sequence containers in the C++ STL:

std::vector:

std::vector is a dynamic array that can resize automatically when elements are added or removed.
It provides constant time access (O(1)) to elements using indexes and amortized constant time insertion and deletion at the end.
std::vector is a popular choice for general-purpose storage when the size of the container is not known in advance.

std::deque:

std::deque (short for double-ended queue) is similar to std::vector, but it allows efficient insertion and deletion at both ends of the container.
It provides constant time access to elements using indexes, but insertion and deletion at the beginning or end of the deque are also constant time operations (O(1)).
std::deque is suitable when you need to frequently insert or remove elements at both ends.

std::list:

std::list is a doubly linked list that provides constant time insertion and deletion of elements anywhere in the container.
Unlike vectors and deques, std::list does not provide constant time access using indexes. Instead, it requires traversing the list from the beginning or end to access an element.
std::list is efficient for insertions and deletions but may have slower access times due to its linked-list nature.

std::forward_list:

std::forward_list is a singly linked list that allows constant time insertion and deletion at the beginning of the container.
It does not provide constant time access using indexes and requires traversing the list from the beginning to access elements.
std::forward_list is useful when you primarily need to insert and delete elements at the front of the list.

Example of Sequence Container:

Let’s demonstrate the usage of std::vector, a sequence container, to store and manipulate a collection of integers.

Code:

#include <iostream>
#include <vector>

int main() {
    // Create a vector to store integers
    std::vector<int> myVector;

    // Add elements to the vector
    myVector.push_back(10);
    myVector.push_back(20);
    myVector.push_back(30);
    myVector.push_back(40);

    // Access elements using index
    std::cout << "Elements in the vector:" << std::endl;
    for (size_t i = 0; i < myVector.size(); ++i) {
        std::cout << myVector[i] << " ";
    }
    std::cout << std::endl;

    // Iterate through the vector using a range-based for loop
    std::cout << "Using range-based for loop:" << std::endl;
    for (const int& num : myVector) {
        std::cout << num << " ";
    }
    std::cout << std::endl;

    return 0;
}

Output:

Elements in the vector:
10 20 30 40 
Using range-based for loop:
10 20 30 40

Explanation of the Code:
In this example, we use the std::vector sequence container from the STL:

We create a vector called myVector, which can store integers (int).
We add elements to the vector using the push_back method, which adds elements at the end of the vector.
We access elements in the vector using an index in a loop and display them.
We iterate through the vector using a range-based for loop and display its elements.

The output shows the elements stored in the vector and the result of iterating through the vector using the range-based for loop.

Applications of Sequence Containers:

Sequence containers are widely used in C++ for various purposes, including:

Storing and managing collections of data elements.
Implementing data structures like stacks, queues, and linked lists.
Working with data that requires dynamic resizing and efficient access to elements.
Implementing algorithms that require efficient insertion and deletion of elements.

Pros and Cons of Sequence Containers:

Pros:

Constant time access: Sequence containers like std::vector and std::deque provide constant time access to elements using indexes.
Efficient resizing: Dynamic resizing makes it easy to manage elements without worrying about the size of the container.
Versatility: Each sequence container offers unique features and capabilities, allowing developers to choose the best-suited container for their specific use case.

Cons:

Memory overhead: Sequence containers may have additional memory overhead compared to arrays due to bookkeeping and dynamic resizing.
Slower access times: Some sequence containers, like std::list and std::forward_list, have slower access