622. Design Circular Queue

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.

# @lc code=start
using LeetCode

mutable struct MyCircularQueue
    len::Int
    front::Int
    rear::Int
    arr::Vector{Int} ## use one extra position
    MyCircularQueue(k::Int)  = new(k + 1, 1, 1, Vector{Int}(undef, k + 1))
end

is_full(que::MyCircularQueue) = (que.rear + 1 - que.front) % que.len == 0

function en_queue(que::MyCircularQueue, val::Int)
    is_full(que) && return false
    que.arr[que.rear] = val
    que.rear = que.rear % que.len + 1
    return true
end

is_empty(que::MyCircularQueue) = que.front == que.rear

function de_queue(que::MyCircularQueue)
    is_empty(que) && return false
    que.front = que.front % que.len + 1
    return true
end

front(que::MyCircularQueue) = is_empty(que) ? -1 : que.arr[que.front]
function rear(que::MyCircularQueue)
    is_empty(que) && return -1
    return que.arr[mod(que.rear - 2, que.len) + 1] ## use mod instead of % to avoid negative number
end

# @lc code=end

rear (generic function with 1 method)

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