设计实现双端队列。
你的实现需要支持以下操作：
MyCircularDeque(k)：构造函数,双端队列的大小为k。
insertFront()：将一个元素添加到双端队列头部。 如果操作成功返回 true。
insertLast()：将一个元素添加到双端队列尾部。如果操作成功返回 true。
deleteFront()：从双端队列头部删除一个元素。 如果操作成功返回 true。
deleteLast()：从双端队列尾部删除一个元素。如果操作成功返回 true。
getFront()：从双端队列头部获得一个元素。如果双端队列为空，返回 -1。
getRear()：获得双端队列的最后一个元素。 如果双端队列为空，返回 -1。
isEmpty()：检查双端队列是否为空。
isFull()：检查双端队列是否满了。
示例：
MyCircularDeque circularDeque = new MycircularDeque(3); // 设置容量大小为3
circularDeque.insertLast(1); // 返回 true
circularDeque.insertLast(2); // 返回 true
circularDeque.insertFront(3); // 返回 true
circularDeque.insertFront(4); // 已经满了，返回 false
circularDeque.getRear(); // 返回 2
circularDeque.isFull(); // 返回 true
circularDeque.deleteLast(); // 返回 true
circularDeque.insertFront(4); // 返回 true
circularDeque.getFront(); // 返回 4
提示：
所有值的范围为 [1, 1000]
操作次数的范围为 [1, 1000]
请不要使用内置的双端队列库。
来源：力扣（LeetCode）
链接：https://leetcode-cn.com/problems/design-circular-deque
著作权归领扣网络所有。商业转载请联系官方授权，非商业转载请注明出处。
算法
swift
class MyCircularDeque {
var deque: [Int]
var capacity: Int // 大小
var front: Int // 头指针，第一个元素的索引
var rear: Int // 尾指针，最后一个元素的下一个索引
/** Initialize your data structure here. Set the size of the deque to be k. */
init(_ k: Int) {
// 大小多一，避免循环双端队列为 空 和 满 时无法判断
capacity = k + 1
deque = [Int](repeating: 0, count: capacity)
front = 0
rear = 0
}
/** Checks whether the circular deque is empty or not. */
func isEmpty() -> Bool {
return front == rear
}
/** Checks whether the circular deque is full or not. */
func isFull() -> Bool {
if front == (rear + 1) % capacity {
return true
}
return false
}
/** Adds an item at the front of Deque. Return true if the operation is successful. */
func insertFront(_ value: Int) -> Bool {
if isFull() {
return false
}
// 头插，先向前移动 头指针，再插入数据
front = (front - 1 + capacity) % capacity
deque[front] = value
return true
}
/** Adds an item at the rear of Deque. Return true if the operation is successful. */
func insertLast(_ value: Int) -> Bool {
if isFull() {
return false
}
// 尾插，先插入数据，再向后移动尾指针
deque[rear] = value
rear = (rear + 1) % capacity
return true
}
/** Deletes an item from the front of Deque. Return true if the operation is successful. */
func deleteFront() -> Bool {
if isEmpty() {
return false
}
// 头指针向前移动
front = (front + 1) % capacity
return true
}
/** Deletes an item from the rear of Deque. Return true if the operation is successful. */
func deleteLast() -> Bool {
if isEmpty() {
return false
}
// 尾指针向后移动
rear = (rear - 1 + capacity) % capacity
return true
}
/** Get the front item from the deque. */
func getFront() -> Int {
if isEmpty() {
return -1
}
return deque[front]
}
/** Get the last item from the deque. */
func getRear() -> Int {
if isEmpty() {
return -1
}
// 尾指针指向索引是null，取尾指针索引元素时，取尾指针的前一个
return deque[(rear - 1 + capacity) % capacity]
}
}
/**
* Your MyCircularDeque object will be instantiated and called as such:
* let obj = MyCircularDeque(k)
* let ret_1: Bool = obj.insertFront(value)
* let ret_2: Bool = obj.insertLast(value)
* let ret_3: Bool = obj.deleteFront()
* let ret_4: Bool = obj.deleteLast()
* let ret_5: Int = obj.getFront()
* let ret_6: Int = obj.getRear()
* let ret_7: Bool = obj.isEmpty()
* let ret_8: Bool = obj.isFull()
*/
Java
/*
* @lc app=leetcode.cn id=641 lang=java
*
* [641] 设计循环双端队列
*/
// @lc code=start
class MyCircularDeque {
private int front;
private int rear;
private int capacity;
private int[] deque;
/** Initialize your data structure here. Set the size of the deque to be k. */
public MyCircularDeque(int k) {
capacity = k + 1;
deque = new int[capacity];
front = 0;
rear = 0;
}
/** Adds an item at the front of Deque. Return true if the operation is successful. */
public boolean insertFront(int value) {
if (isFull()) {
return false;
} else {
front = (front - 1 + capacity) % capacity;
deque[front] = value;
return true;
}
}
/** Adds an item at the rear of Deque. Return true if the operation is successful. */
public boolean insertLast(int value) {
if (isFull()) {
return false;
} else {
deque[rear] = value;
rear = (rear + 1) % capacity;
return true;
}
}
/** Deletes an item from the front of Deque. Return true if the operation is successful. */
public boolean deleteFront() {
if (isEmpty()) {
return false;
} else {
front = (front + 1) % capacity;
return true;
}
}
/** Deletes an item from the rear of Deque. Return true if the operation is successful. */
public boolean deleteLast() {
if (isEmpty()) {
return false;
} else {
rear = (rear - 1 + capacity) % capacity;
return true;
}
}
/** Get the front item from the deque. */
public int getFront() {
if (isEmpty()) {
return -1;
}
return deque[front];
}
/** Get the last item from the deque. */
public int getRear() {
if (isEmpty()) {
return -1;
}
return deque[(rear - 1 + capacity) % capacity];
}
/** Checks whether the circular deque is empty or not. */
public boolean isEmpty() {
return rear == front;
}
/** Checks whether the circular deque is full or not. */
public boolean isFull() {
return (rear + 1) % capacity == front;
}
}
/**
* 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();
*/
