DesignCircularDeque.java

package medium;

/**
 * ClassName: DesignCircularDeque.java
 * Author: chenyiAlone
 * Create Time: 2019/11/7 14:36
 * Description: No.641 Design Circular Deque
 *
 * Design your implementation of the circular double-ended queue (deque).
 *
 * Your implementation should support following operations:
 *
 * MyCircularDeque(k): Constructor, set the size of the deque to be k.
 * insertFront(): Adds an item at the front of Deque. Return true if the operation is successful.
 * insertLast(): Adds an item at the rear of Deque. Return true if the operation is successful.
 * deleteFront(): Deletes an item from the front of Deque. Return true if the operation is successful.
 * deleteLast(): Deletes an item from the rear of Deque. Return true if the operation is successful.
 * getFront(): Gets the front item from the Deque. If the deque is empty, return -1.
 * getRear(): Gets the last item from Deque. If the deque is empty, return -1.
 * isEmpty(): Checks whether Deque is empty or not. 
 * isFull(): Checks whether Deque is full or not.
 *  
 *
 * Example:
 *
 * MyCircularDeque circularDeque = new MycircularDeque(3); // set the size to be 3
 * circularDeque.insertLast(1);			// return true
 * circularDeque.insertLast(2);			// return true
 * circularDeque.insertFront(3);			// return true
 * circularDeque.insertFront(4);			// return false, the queue is full
 * circularDeque.getRear();  			// return 2
 * circularDeque.isFull();				// return true
 * circularDeque.deleteLast();			// return true
 * circularDeque.insertFront(4);			// return true
 * circularDeque.getFront();			// return 4
 *  
 *
 * Note:
 *
 * All values will be in the range of [0, 1000].
 * The number of operations will be in the range of [1, 1000].
 * Please do not use the built-in Deque library.
 *
 *
 */
public class DesignCircularDeque {
    private class Node {
        Node prev, next;
        int val;
        Node() {}
        Node(int val) {
            this.val = val;
        }
    }

    private Node head, tail;
    private int size, capacity;

    /** Initialize your data structure here. Set the size of the deque to be k. */
    public DesignCircularDeque(int k) {
        head = new Node();
        tail = new Node();
        head.next = tail;
        tail.prev = head;
        capacity = k;
        size = 0;
    }

    /** Adds an item at the front of Deque. Return true if the operation is successful. */
    public boolean insertFront(int value) {
        if (size == capacity) return false;
        Node t = new Node(value);
        Node next = head.next;
        t.next = next;
        t.prev = head;
        head.next = t;
        next.prev = t;
        size++;
        return true;
    }

    /** Adds an item at the rear of Deque. Return true if the operation is successful. */
    public boolean insertLast(int value) {
        if (size == capacity) return false;
        Node t = new Node(value);
        Node prev = tail.prev;
        t.prev = prev;
        t.next = tail;
        prev.next = t;
        tail.prev = t;
        size++;
        return true;
    }

    /** Deletes an item from the front of Deque. Return true if the operation is successful. */
    public boolean deleteFront() {
        if (size == 0) return false;
        head.next = head.next.next;
        head.next.prev = head;
        size--;
        return true;
    }

    /** Deletes an item from the rear of Deque. Return true if the operation is successful. */
    public boolean deleteLast() {
        if (size == 0) return false;
        tail.prev = tail.prev.prev;
        tail.prev.next = tail;
        size--;
        return true;
    }

    /** Get the front item from the deque. */
    public int getFront() {
        if (size == 0) return -1;
        return head.next.val;
    }

    /** Get the last item from the deque. */
    public int getRear() {
        if (size == 0) return -1;
        return tail.prev.val;
    }

    /** Checks whether the circular deque is empty or not. */
    public boolean isEmpty() {
        return size == 0;
    }

    /** Checks whether the circular deque is full or not. */
    public boolean isFull() {
        return size == capacity;
    }
}