circular queue added

Contributors.md

@@ -38,3 +38,4 @@
 * [Muskan](https://github.com/Muskan-goyal6)
 * [Tarannum](https://github.com/giTan7)
 * [HCamberos](https://github.com/HCamberos)
+* [Igor](https://github.com/IgorBizyanov)

Queue/queue.cpp

@@ -0,0 +1,121 @@
+#include <iostream>
+#include <stdlib.h>
+
+using namespace std;
+
+template <typename T>
+class CircularQueue {
+public:
+
+    CircularQueue(int k) {
+        size = k;
+        buffer = (T*)malloc(sizeof(T)*k);
+        head = -1; 
+        tail = -1; 
+    }
+
+    /*
+        This function inserts an element into CircularQueue
+        Args:
+            - int value: value to be inserted
+    */
+    bool enQueue(T value) {
+        if (isFull()){
+
+            return false;
+        }
+        cout << "DEBUG size == 0 or Full" << endl;
+
+        if (isEmpty()) {
+            head = 0;
+            tail = 0;    
+        }
+
+        else 
+            tail = (tail + 1) % size;
+
+        buffer[tail] = value;
+        return true;
+    }
+
+    /** Delete an element from the circular queue. Return true if the operation is successful. */
+    bool deQueue() {
+        if (isEmpty())
+            return false;
+
+        buffer[head] = 0;
+        if (head == tail) {
+            head = tail = -1;
+        }
+        else
+            head = (head + 1) % size;
+
+        return true;
+    }
+
+    /** Get the front item from the queue. */
+    T Head() {
+        return buffer[head];
+    }
+
+    /** Get the last item from the queue. */
+    T Tail() {
+        return buffer[tail];
+    }
+
+
+    void print() {
+
+        for (int i = 0; i < size; ++i) {
+            cout << buffer[i] << " ";
+        }
+        cout << endl;
+        cout << "head = " << head << " tail = " << tail << endl;
+    }
+
+private:
+
+    T *buffer;
+    int size;
+    int head; 
+    int tail; 
+
+    bool isEmpty() {
+        return (head == -1 && tail == -1);
+    }
+
+    bool isFull() {
+        return  size == 0 || head == ((tail+1) % size);
+    }
+
+};
+
+/*Usage: 
+	en x : enqueue x number to the end of our queue
+	de   : dequeue head number
+
+*/
+int main() {
+    string command;
+    double key;
+    CircularQueue <double>qu = CircularQueue<double>(6);
+
+    while (true) {
+
+        cin >> command;
+        if (command == "en") {
+            cin >> key;
+            qu.enQueue(key);
+            qu.print();
+        }
+        if (command == "de") {
+            qu.deQueue();
+            qu.print();
+        }
+
+        if (command == "exit")
+            break;
+    }
+
+    return 0;
+}