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package g0601_0700.s0622_design_circular_queue;

// #Medium #Array #Design #Linked_List #Queue #Programming_Skills_II_Day_20
// #2022_03_21_Time_3_ms_(100.00%)_Space_42.8_MB_(83.38%)

/**
 * 622 - Design Circular Queue\.
 *
 * Medium
 *
 * Design your implementation of the circular queue. The circular queue is a linear data structure in which the operations are performed based on FIFO (First In First Out) principle and the last position is connected back to the first position to make a circle. It is also called "Ring Buffer".
 *
 * One of the benefits of the circular queue is that we can make use of the spaces in front of the queue. In a normal queue, once the queue becomes full, we cannot insert the next element even if there is a space in front of the queue. But using the circular queue, we can use the space to store new values.
 *
 * Implementation the `MyCircularQueue` class:
 *
 * *   `MyCircularQueue(k)` Initializes the object with the size of the queue to be `k`.
 * *   `int Front()` Gets the front item from the queue. If the queue is empty, return `-1`.
 * *   `int Rear()` Gets the last item from the queue. If the queue is empty, return `-1`.
 * *   `boolean enQueue(int value)` Inserts an element into the circular queue. Return `true` if the operation is successful.
 * *   `boolean deQueue()` Deletes an element from the circular queue. Return `true` if the operation is successful.
 * *   `boolean isEmpty()` Checks whether the circular queue is empty or not.
 * *   `boolean isFull()` Checks whether the circular queue is full or not.
 *
 * You must solve the problem without using the built-in queue data structure in your programming language.
 *
 * **Example 1:**
 *
 * **Input** ["MyCircularQueue", "enQueue", "enQueue", "enQueue", "enQueue", "Rear", "isFull", "deQueue", "enQueue", "Rear"] [[3], [1], [2], [3], [4], [], [], [], [4], []]
 *
 * **Output:** [null, true, true, true, false, 3, true, true, true, 4]
 *
 * **Explanation:** MyCircularQueue myCircularQueue = new MyCircularQueue(3); myCircularQueue.enQueue(1); // return True myCircularQueue.enQueue(2); // return True myCircularQueue.enQueue(3); // return True myCircularQueue.enQueue(4); // return False myCircularQueue.Rear(); // return 3 myCircularQueue.isFull(); // return True myCircularQueue.deQueue(); // return True myCircularQueue.enQueue(4); // return True myCircularQueue.Rear(); // return 4
 *
 * **Constraints:**
 *
 * *   `1 <= k <= 1000`
 * *   `0 <= value <= 1000`
 * *   At most `3000` calls will be made to `enQueue`, `deQueue`, `Front`, `Rear`, `isEmpty`, and `isFull`.
**/
public class MyCircularQueue {
    private final DoubleLinkedNode dumyHead = new DoubleLinkedNode(0);
    private final int maxSize;
    private int size = 0;

    public MyCircularQueue(int k) {
        this.maxSize = k;
        dumyHead.left = dumyHead;
        dumyHead.right = dumyHead;
    }

    public boolean enQueue(int value) {
        if (size == maxSize) {
            return false;
        }
        DoubleLinkedNode node = new DoubleLinkedNode(value);
        DoubleLinkedNode right = dumyHead.right;
        dumyHead.right = node;
        node.left = dumyHead;
        node.right = right;
        right.left = node;
        size++;
        return true;
    }

    public boolean deQueue() {
        if (size == 0) {
            return false;
        }
        DoubleLinkedNode left = dumyHead.left;
        dumyHead.left = left.left;
        dumyHead.left.right = dumyHead;
        size--;
        return true;
    }

    public int rear() {
        if (size == 0) {
            return -1;
        }
        return dumyHead.right.val;
    }

    public int front() {
        if (size == 0) {
            return -1;
        }
        return dumyHead.left.val;
    }

    public boolean isEmpty() {
        return size == 0;
    }

    public boolean isFull() {
        return size == maxSize;
    }

    static class DoubleLinkedNode {
        private final int val;
        private DoubleLinkedNode left;
        private DoubleLinkedNode right;

        public DoubleLinkedNode(int val) {
            this.val = val;
        }
    }
}

/*
 * Your MyCircularQueue object will be instantiated and called as such:
 * MyCircularQueue obj = new MyCircularQueue(k);
 * boolean param_1 = obj.enQueue(value);
 * boolean param_2 = obj.deQueue();
 * int param_3 = obj.front();
 * int param_4 = obj.rear();
 * boolean param_5 = obj.isEmpty();
 * boolean param_6 = obj.isFull();
 */