【数据结构】算法 Design Circular Queue 设计循环队列

目录

• Design Circular Queue 设计循环队列
  • Description
  • 思路:

Design Circular Queue 设计循环队列

Description

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.

Implementation the MyCircularQueue class:

• MyCircularQueue(k) Initializes the object with the size of the queue to be k.
• int Front() Gets the front item from the queue. If the queue is empty, return -1.
• int Rear() Gets the last item from the queue. If the queue is empty, return -1.
• boolean enQueue(int value) Inserts an element into the circular queue. Return true if the operation is successful.
• boolean deQueue() Deletes an element from the circular queue. Return true if the operation is successful.
• boolean isEmpty() Checks whether the circular queue is empty or not.
• boolean isFull() Checks whether the circular queue is full or not.

设计循环的队列

思路:

使用数组，head为首节点，tail为尾节点后一个节点，cnt为队列元素个数

 class MyCircularQueue {

    public  int head = 0;
    public  int tail =0 ;
    public  int cnt =0;
    public int[] arr ;
    public MyCircularQueue(int k) {
           arr = new int[k];
           head = 0;
           tail =0 ;
           cnt =0;
    }
    
    
    public boolean enQueue(int value) {
        if(isFull()){
            return false;
        }
        arr[tail] = value;
        tail = (tail +1 ) % arr.length;
        cnt+=1;
        return true;
    }
    
    public boolean deQueue() {
        if(isEmpty()){
            return false;
        }
        head = (head +1 ) % arr.length; 
        cnt-=1;
        return true;

    }
    
    public int Front() {
        if(isEmpty()){
            return -1;
        }
        return arr[head];
    }
    
    public int Rear() {
        if(isEmpty()){
            return -1;
        }
        return arr[(tail-1+arr.length)%arr.length];
    }
    
    public boolean isEmpty() {
        if(cnt==0){
            return true;
        }
        else{
            return false;
        }
        
    }
    
    public boolean isFull() {
        
        if(cnt==arr.length){
            return true;
        }
        else{
            return false;
        }
    }
}

/**
 * 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();
 */