【LeetCode622】设计环形队列

【LeetCode622】设计环形队列

题目描述

提交结果

代码实现

class MyCircularQueue { private int size ; private int head ; private int tail ; private int[] arr; /** Initialize your data structure here. Set the size of the queue to be k. */ public MyCircularQueue(int k) { arr = new int[k]; } /** Insert an element into the circular queue. Return true if the operation is successful. */ public boolean enQueue(int value) { if(size == arr.length){ return false; } arr[tail] = value; tail = tail == arr.length - 1 ? 0 : tail + 1; size++; return true; } /** Delete an element from the circular queue. Return true if the operation is successful. */ public boolean deQueue() { if(size <= 0){ return false; } head = head == arr.length ? 0 : head + 1; size--; return true; } /** Get the front item from the queue. */ public int Front() { if(size == 0){ return -1; } return arr[head]; } /** Get the last item from the queue. */ public int Rear() { if(size == 0){ return -1; } if(tail == 0){ return arr[arr.length - 1]; } return arr[tail - 1]; } /** Checks whether the circular queue is empty or not. */ public boolean isEmpty() { return size == 0; } /** Checks whether the circular queue is full or not. */ public boolean isFull() { return size == arr.length; } }

维护一个首尾指针，head，tail。

维护环形的关键就是，tail == arr.length - 1 ，head == arr.length - 1，时就回到数组开始位置即可。

维护一个size变量相对来说比较简单，来存储队列中的元素个数。否则很难统计出当前队列中的元素个数。