#### Queue Using Array

```/**
* @file
* @brief Implementation of Linear [Queue using array]
* (https://www.geeksforgeeks.org/array-implementation-of-queue-simple/).
* @details
* The Linear Queue is a data structure used for holding a sequence of
* values, which can be added to the end line (enqueue), removed from
* head of line (dequeue) and displayed.
* ### Algorithm
* Values can be added by increasing the `rear` variable by 1 (which points to
* the end of the array), then assigning new value to `rear`'s element of the
* array.
*
* Values can be removed by increasing the `front` variable by 1 (which points
* to the first of the array), so it cannot reached any more.
*
* @author [Pooja](https://github.com/pooja-git11)
*/
#include <array>     /// for std::array
#include <iostream>  /// for io operations

constexpr uint16_t max_size{10};  ///< Maximum size of the queue

/**
* @namespace data_structures
* @brief Algorithms with data structures
*/
namespace data_structures {

/**
* @namespace queue_using_array
* @brief Functions for [Queue using Array]
* (https://www.geeksforgeeks.org/array-implementation-of-queue-simple/)
* implementation.
*/
namespace queue_using_array {

/**
* @brief Queue_Array class containing the main data and also index of head and
* tail of the array.
*/
class Queue_Array {
public:
void enqueue(const int16_t&);  ///< Add element to the first of the queue
int dequeue();                 ///< Delete element from back of the queue
void display() const;          ///< Show all saved data
private:
int8_t front{-1};                     ///< Index of head of the array
int8_t rear{-1};                      ///< Index of tail of the array
std::array<int16_t, max_size> arr{};  ///< All stored data
};

/**
* @brief Adds new element to the end of the queue
* @param ele to be added to the end of the queue
*/
void Queue_Array::enqueue(const int16_t& ele) {
if (rear == arr.size() - 1) {
std::cout << "\nStack is full";
} else if (front == -1 && rear == -1) {
front = 0;
rear = 0;
arr[rear] = ele;
} else if (rear < arr.size()) {
++rear;
arr[rear] = ele;
}
}

/**
* @brief Remove element that is located at the first of the queue
* @returns data that is deleted if queue is not empty
*/
int Queue_Array::dequeue() {
int8_t d{0};
if (front == -1) {
std::cout << "\nstack is empty ";
return 0;
} else if (front == rear) {
d = arr.at(front);
front = rear = -1;
} else {
d = arr.at(front++);
}

return d;
}

/**
* @brief Utility function to show all elements in the queue
*/
void Queue_Array::display() const {
if (front == -1) {
std::cout << "\nStack is empty";
} else {
for (int16_t i{front}; i <= rear; ++i) std::cout << arr.at(i) << " ";
}
}

}  // namespace queue_using_array
}  // namespace data_structures

/**
* @brief Main function
* @details
* Allows the user to add and delete values from the queue.
* Also allows user to display values in the queue.
* @returns 0 on exit
*/
int main() {
int op{0}, data{0};
data_structures::queue_using_array::Queue_Array ob;

std::cout << "\n1. enqueue(Insertion) ";
std::cout << "\n2. dequeue(Deletion)";
std::cout << "\n3. Display";
std::cout << "\n4. Exit";
while (true) {
std::cout << "\nEnter your choice ";
std::cin >> op;
if (op == 1) {
std::cout << "Enter data  ";
std::cin >> data;
ob.enqueue(data);
} else if (op == 2) {
data = ob.dequeue();
std::cout << "\ndequeue element is:\t" << data;
} else if (op == 3) {
ob.display();
} else if (op == 4) {
exit(0);
} else {
std::cout << "\nWrong choice ";
}
}

return 0;
}
```