标签:arr return 队列 环形 queue enQueue int front
622. Design Circular Queue MediumDesign 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 bek
.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. Returntrue
if the operation is successful.boolean deQueue()
Deletes an element from the circular queue. Returntrue
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.
You must solve the problem without using the built-in queue data structure in your programming language.
Example 1:
Input ["MyCircularQueue", "enQueue", "enQueue", "enQueue", "enQueue", "Rear", "isFull", "deQueue", "enQueue", "Rear"] [[3], [1], [2], [3], [4], [], [], [], [4], []] Output [null, true, true, true, false, 3, true, true, true, 4] Explanation MyCircularQueue myCircularQueue = new MyCircularQueue(3); myCircularQueue.enQueue(1); // return True myCircularQueue.enQueue(2); // return True myCircularQueue.enQueue(3); // return True myCircularQueue.enQueue(4); // return False myCircularQueue.Rear(); // return 3 myCircularQueue.isFull(); // return True myCircularQueue.deQueue(); // return True myCircularQueue.enQueue(4); // return True myCircularQueue.Rear(); // return 4
Constraints:
1 <= k <= 1000
0 <= value <= 1000
- At most
3000
calls will be made toenQueue
,deQueue
,Front
,Rear
,isEmpty
, andisFull
.
解法:
1.如何判定队列是满的,如何判定队列是空的? 很巧妙的增加了一个空位来确保
2.rear和front每次++后要取模保证永远在界内
class MyCircularQueue { private int[] arr; private int front=0,rear=0; public MyCircularQueue(int k) { arr = new int[k+1]; } public boolean enQueue(int value) { if(isFull()) return false; arr[rear]=value; rear=(rear+1)%arr.length; return true; } public boolean deQueue() { if(isEmpty()) return false; front=(front+1)%arr.length; return true; } public int Front() { if(isEmpty()) return -1; return arr[front]; } public int Rear() { if(isEmpty()) return -1; return arr[(rear-1+arr.length)%arr.length]; } public boolean isEmpty() { return (rear-front+arr.length)%arr.length==0; } public boolean isFull() { return (rear+1)%arr.length==front; } }
标签:arr,return,队列,环形,queue,enQueue,int,front 来源: https://www.cnblogs.com/cynrjy/p/15862433.html
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