622.design-circular-queue.java

/*
 * @lc app=leetcode id=622 lang=java
 *
 * [622] Design Circular Queue
 *
 * https://leetcode.com/problems/design-circular-queue/description/
 *
 * algorithms
 * Medium (38.21%)
 * Total Accepted:    20.5K
 * Total Submissions: 53.3K
 * Testcase Example:  '["MyCircularQueue","enQueue","enQueue","enQueue","enQueue","Rear","isFull","deQueue","enQueue","Rear"]\n[[3],[1],[2],[3],[4],[],[],[],[4],[]]'
 *
 * 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.
 *
 * Your implementation should support following operations:
 *
 *
 * MyCircularQueue(k): Constructor, set the size of the queue to be k.
 * Front: Get the front item from the queue. If the queue is empty, return
 * -1.
 * Rear: Get the last item from the queue. If the queue is empty, return
 * -1.
 * enQueue(value): Insert an element into the circular queue. Return true if
 * the operation is successful.
 * deQueue(): Delete an element from the circular queue. Return true if the
 * operation is successful.
 * isEmpty(): Checks whether the circular queue is empty or not.
 * isFull(): Checks whether the circular queue is full or not.
 *
 *
 *
 *
 * Example:
 *
 *
 * MyCircularQueue circularQueue = new MyCircularQueue(3); // set the size to
 * be 3
 * circularQueue.enQueue(1);  // return true
 * circularQueue.enQueue(2);  // return true
 * circularQueue.enQueue(3);  // return true
 * circularQueue.enQueue(4);  // return false, the queue is full
 * circularQueue.Rear();  // return 3
 * circularQueue.isFull();  // return true
 * circularQueue.deQueue();  // return true
 * circularQueue.enQueue(4);  // return true
 * circularQueue.Rear();  // 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 Queue library.
 *
 *
 */
class MyCircularQueue {
  private int[] data;
  private int head;
  private int tail;
  private int size;

  /** Initialize your data structure here. Set the size of the queue to be k. */
  public MyCircularQueue(int k) {
    data = new int[k];
    size = k;
    head = -1;
    tail = -1;
  }

  /** Insert an element into the circular queue. Return true if the operation is successful. */
  public boolean enQueue(int value) {
    if (isFull()) {
      return false;
    }
    if (isEmpty()) {
      head = 0;
    }
    tail = (tail + 1) % size;
    data[tail] = value;
    return true;
  }

  /** Delete an element from the circular queue. Return true if the operation is successful. */
  public boolean deQueue() {
    if (isEmpty()) {
      return false;
    }
    if (head == tail) {
      head = -1;
      tail = -1;
      return true;
    }
    head = (head + 1) % size;
    return true;
  }

  /** Get the front item from the queue. */
  public int Front() {
    if (isEmpty()) {
      return -1;
    }
    return data[head];
  }

  /** Get the last item from the queue. */
  public int Rear() {
    if (isEmpty()) {
      return -1;
    }
    return data[tail];
  }

  /** Checks whether the circular queue is empty or not. */
  public boolean isEmpty() {
    return head == -1;
  }

  /** Checks whether the circular queue is full or not. */
  public boolean isFull() {
    return ((tail + 1) % size) == head;
  }
}

/**
 * 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();
 */