Design Circular Queue
Similar Problems:
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.
Github: code.dennyzhang.com
Credits To: leetcode.com
Leave me comments, if you have better ways to solve.
- Solution:
// Blog link: https://code.dennyzhang.com/design-circular-queue // Basic Ideas: Use an Array // Differentiate two cases: full or empty // Two pointers: front, rear // The cell of rear won't store any items. // When rear == front -> empty // When (rear+1)%n == front -> full // Complexity: Time O(1), Space O(n) type MyCircularQueue struct { l []int front, rear, size int } /** Initialize your data structure here. Set the size of the queue to be k. */ func Constructor(k int) MyCircularQueue { queue := MyCircularQueue{} queue.l = make([]int, k+1) queue.front, queue.rear, queue.size = 0, 0, k+1 return queue } /** Insert an element into the circular queue. Return true if the operation is successful. */ func (this *MyCircularQueue) EnQueue(value int) bool { if this.IsFull() { return false } this.l[this.rear] = value this.rear = (this.rear+1) % this.size return true } /** Delete an element from the circular queue. Return true if the operation is successful. */ func (this *MyCircularQueue) DeQueue() bool { if this.IsEmpty() { return false } this.front = (this.front+1+this.size) % this.size return true } /** Get the front item from the queue. */ func (this *MyCircularQueue) Front() int { if this.IsEmpty() { return -1 } return this.l[this.front] } /** Get the last item from the queue. */ func (this *MyCircularQueue) Rear() int { if this.IsEmpty() { return -1 } return this.l[(this.rear-1+this.size) % this.size] } /** Checks whether the circular queue is empty or not. */ func (this *MyCircularQueue) IsEmpty() bool { return this.rear == this.front } /** Checks whether the circular queue is full or not. */ func (this *MyCircularQueue) IsFull() bool { return (this.rear+1) % this.size == this.front } /** * Your MyCircularQueue object will be instantiated and called as such: * obj := Constructor(k); * param_1 := obj.EnQueue(value); * param_2 := obj.DeQueue(); * param_3 := obj.Front(); * param_4 := obj.Rear(); * param_5 := obj.IsEmpty(); * param_6 := obj.IsFull(); */
