chore: import upstream snapshot with attribution

data_structures/queue_using_array.cpp

@@ -0,0 +1,140 @@
+/**
+ * @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)
+ * @author [Farbod Ahmadian](https://github.com/farbodahm)
+ */
+#include <array>     /// for std::array
+#include <cstdint>
+#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;
+}