# 622. Design Circular Queue

• Time: $O(1)$
• Space: $O(k)$
  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 class MyCircularQueue { public: /** Initialize your data structure here. Set the size of the queue to be k. */ MyCircularQueue(int k) : k(k), q(k), rear(k - 1) {} /** Insert an element into the circular queue. Return true if the operation is * successful. */ bool enQueue(int value) { if (isFull()) return false; rear = ++rear % k; q[rear] = value; ++size; return true; } /** Delete an element from the circular queue. Return true if the operation is * successful. */ bool deQueue() { if (isEmpty()) return false; front = ++front % k; --size; return true; } /** Get the front item from the queue. */ int Front() { return isEmpty() ? -1 : q[front]; } /** Get the last item from the queue. */ int Rear() { return isEmpty() ? -1 : q[rear]; } /** Checks whether the circular queue is empty or not. */ bool isEmpty() { return size == 0; } /** Checks whether the circular queue is full or not. */ bool isFull() { return size == k; } private: const int k; vector q; int size = 0; int front = 0; int rear; }; 
  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 class MyCircularQueue { /** Initialize your data structure here. Set the size of the queue to be k. */ public MyCircularQueue(int k) { this.k = k; this.q = new int[k]; this.rear = k - 1; } /** Insert an element into the circular queue. Return true if the operation is successful. */ public boolean enQueue(int value) { if (isFull()) return false; rear = ++rear % k; q[rear] = value; ++size; return true; } /** Delete an element from the circular queue. Return true if the operation is successful. */ public boolean deQueue() { if (isEmpty()) return false; front = ++front % k; --size; return true; } /** Get the front item from the queue. */ public int Front() { return isEmpty() ? -1 : q[front]; } /** Get the last item from the queue. */ public int Rear() { return isEmpty() ? -1 : q[rear]; } /** Checks whether the circular queue is empty or not. */ public boolean isEmpty() { return size == 0; } /** Checks whether the circular queue is full or not. */ public boolean isFull() { return size == k; } private final int k; private int[] q; private int size = 0; private int front = 0; private int rear; }