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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 bek
.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. Returntrue
if the operation is successful.deQueue()
: Delete an element from the circular queue. Returntrue
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 3circularQueue.enQueue(1); // return truecircularQueue.enQueue(2); // return truecircularQueue.enQueue(3); // return truecircularQueue.enQueue(4); // return false, the queue is fullcircularQueue.Rear(); // return 3circularQueue.isFull(); // return truecircularQueue.deQueue(); // return truecircularQueue.enQueue(4); // return truecircularQueue.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.
题意:设计循环队列实现。 循环队列是一种线性数据结构,其操作表现基于 FIFO
(先进先出)原则并且队尾被连接在队首之后以形成一个循环。也被称为"环形缓冲器"。循环队列的一个好处是可以利用这个队列之前用过的空间。在一个普通队列里,一旦一个队列"满了",就不能插入下一个元素,即使在队列前面仍有空间。但是使用循环队列,就能使用这些空间去存储新的值。
思路
感觉LeetCode上的设计题都可以替代平常的数据结构实现课程的学习了。代码如下:
class MyCircularQueue { private: int *queue; int capacity; int size; int front, rear; //[front, rear]public: /** Initialize your data structure here. Set the size of the queue to be k. */ MyCircularQueue(int k) { queue = new int[capacity = k]; size = 0; front = 0, rear = -1; } /** Insert an element into the circular queue. Return true if the operation is successful. */ bool enQueue(int value) { if (isFull()) return false; ++size; rear = (rear + 1) % capacity; queue[rear] = value; return true; } /** Delete an element from the circular queue. Return true if the operation is successful. */ bool deQueue() { if (isEmpty()) return false; --size; front = (front + 1) % capacity; return true; } /** Get the front item from the queue. */ int Front() { if (isEmpty()) return -1; return queue[front]; } /** Get the last item from the queue. */ int Rear() { if (isEmpty()) return -1; return queue[rear]; } /** Checks whether the circular queue is empty or not. */ bool isEmpty() { return size == 0; } /** Checks whether the circular queue is full or not. */ bool isFull() { return size == capacity; }};
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