【数据结构】算法 Design Circular Deque 设计循环双端队列

目录

• Design Circular Deque 设计循环双端队列
  • Description
  • 思路:

Design Circular Deque 设计循环双端队列

Description

Design your implementation of the circular double-ended queue (deque).

Your implementation should support following operations:

• MyCircularDeque(k): Constructor, set the size of the deque to be k.
• insertFront(): Adds an item at the front of Deque. Return true if the operation is successful.
• insertLast(): Adds an item at the rear of Deque. Return true if the operation is successful.
• deleteFront(): Deletes an item from the front of Deque. Return true if the operation is successful.
• deleteLast(): Deletes an item from the rear of Deque. Return true if the operation is successful.
• getFront(): Gets the front item from the Deque. If the deque is empty, return -1.
• getRear(): Gets the last item from Deque. If the deque is empty, return -1.
• isEmpty(): Checks whether Deque is empty or not.
• isFull(): Checks whether Deque is full or not.

MyCircularDeque circularDeque = new MycircularDeque(3); // set the size to be 3
circularDeque.insertLast(1);			// return true
circularDeque.insertLast(2);			// return true
circularDeque.insertFront(3);			// return true
circularDeque.insertFront(4);			// return false, the queue is full
circularDeque.getRear();  			// return 2
circularDeque.isFull();				// return true
circularDeque.deleteLast();			// return true
circularDeque.insertFront(4);			// return true
circularDeque.getFront();			// return 4

设计循环双端队列

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 MyCircularDeque {

    public int[] arr;
    public int cnt;
    public int head;
    public int tail;//指向尾元素的下一位

    /** Initialize your data structure here. Set the size of the deque to be k. */
    public MyCircularDeque(int k) {
        arr = new int[k];
        cnt =0;
        head =0;
        tail =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;
        }
        head = (head -1+arr.length)%arr.length;        
        arr[head] = value;         
        cnt+=1;
        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;
        }
        arr[tail] = value;
        tail = (tail +1 ) % arr.length;
        cnt+=1;
        return true;
    }
    
    /** Deletes an item from the front of Deque. Return true if the operation is successful. */
    public boolean deleteFront() {
        if(isEmpty()){
            return false;
        }
        head = (head +1 ) % arr.length; 
        cnt-=1;
        return true;
    }
    
    /** Deletes an item from the rear of Deque. Return true if the operation is successful. */
    public boolean deleteLast() {
        if(isEmpty()){
            return false;
        }
        tail = (tail -1 +arr.length ) % arr.length; 
        cnt-=1;
        return true;
    }
    
    /** Get the front item from the deque. */
    public int getFront() {
        if(isEmpty()){
            return -1;
        }
        return arr[head];
    }
    
    /** Get the last item from the deque. */
    public int getRear() {
        if(isEmpty()){
            return -1;
        }
        return arr[(tail-1+arr.length)%arr.length];
    }
    
    /** Checks whether the circular deque is empty or not. */
    public boolean isEmpty() {
        if(cnt==0){
            return true;
        }
        else{
            return false;
        }
    }
    
    /** Checks whether the circular deque is full or not. */
    public boolean isFull() {
        if(cnt==arr.length){
            return true;
        }
        else{
            return false;
        }
    }
}

/**
 * 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();
 */