641. Design Circular Deque

Problem

Design your implementation of the circular double-ended queue (deque).

Implement the MyCircularDeque class:

• MyCircularDeque(int k) Initializes the deque with a maximum size of k.

• boolean insertFront() Adds an item at the front of Deque. Returns true if the operation is successful, or false otherwise.

• boolean insertLast() Adds an item at the rear of Deque. Returns true if the operation is successful, or false otherwise.

• boolean deleteFront() Deletes an item from the front of Deque. Returns true if the operation is successful, or false otherwise.

• boolean deleteLast() Deletes an item from the rear of Deque. Returns true if the operation is successful, or false otherwise.

• int getFront() Returns the front item from the Deque. Returns -1 if the deque is empty.

• int getRear() Returns the last item from Deque. Returns -1 if the deque is empty.

• boolean isEmpty() Returns true if the deque is empty, or false otherwise.

• boolean isFull() Returns true if the deque is full, or false otherwise.

  Example 1:

Input
["MyCircularDeque", "insertLast", "insertLast", "insertFront", "insertFront", "getRear", "isFull", "deleteLast", "insertFront", "getFront"]
[[3], [1], [2], [3], [4], [], [], [], [4], []]
Output
[null, true, true, true, false, 2, true, true, true, 4]

Explanation
MyCircularDeque myCircularDeque = new MyCircularDeque(3);
myCircularDeque.insertLast(1);  // return True
myCircularDeque.insertLast(2);  // return True
myCircularDeque.insertFront(3); // return True
myCircularDeque.insertFront(4); // return False, the queue is full.
myCircularDeque.getRear();      // return 2
myCircularDeque.isFull();       // return True
myCircularDeque.deleteLast();   // return True
myCircularDeque.insertFront(4); // return True
myCircularDeque.getFront();     // return 4

  Constraints:

• 1 <= k <= 1000

• 0 <= value <= 1000

• At most 2000 calls will be made to insertFront, insertLast, deleteFront, deleteLast, getFront, getRear, isEmpty, isFull.

Solution (Java)

class MyCircularDeque {
    private final int[] data;
    private int front;
    private int rear;
    private int size;

    public MyCircularDeque(int k) {
        data = new int[k];
        front = 0;
        rear = k - 1;
        size = 0;
    }

    public boolean insertFront(int value) {
        if (size == data.length) {
            return false;
        }
        data[front] = value;
        front = (front + 1) % data.length;
        size++;
        return true;
    }

    public boolean insertLast(int value) {
        if (size == data.length) {
            return false;
        }
        data[rear] = value;
        rear = (rear - 1 + data.length) % data.length;
        size++;
        return true;
    }

    public boolean deleteFront() {
        if (size == 0) {
            return false;
        }
        front = (front - 1 + data.length) % data.length;
        size--;
        return true;
    }

    public boolean deleteLast() {
        if (size == 0) {
            return false;
        }
        rear = (rear + 1) % data.length;
        size--;
        return true;
    }

    public int getFront() {
        if (size == 0) {
            return -1;
        }

        return data[(front - 1 + data.length) % data.length];
    }

    public int getRear() {
        if (size == 0) {
            return -1;
        }
        return data[(rear + 1) % data.length];
    }

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

    public boolean isFull() {
        return size == data.length;
    }
}

/**
 * Your MyCircularDeque object will be instantiated and called as such:
 * MyCircularDeque obj = new MyCircularDeque(k);
 * boolean param_1 = obj.insertFront(value);
 * boolean param_2 = obj.insertLast(value);
 * boolean param_3 = obj.deleteFront();
 * boolean param_4 = obj.deleteLast();
 * int param_5 = obj.getFront();
 * int param_6 = obj.getRear();
 * boolean param_7 = obj.isEmpty();
 * boolean param_8 = obj.isFull();
 */

Explain:

nope.

Complexity:

• Time complexity : O(n).
• Space complexity : O(n).