622. 设计循环队列

https://leetcode-cn.com/problems/design-circular-queue/

Java

/*
 * @Author: Goog Tech
 * @Date: 2020-09-07 08:16:03
 * @LastEditTime: 2020-09-07 08:16:33
 * @Description: https://leetcode-cn.com/problems/design-circular-queue/
 * @FilePath: \leetcode-googtech\#622. Design Circular Queue\Solution.java
 * @WebSite: https://algorithm.show/
 */

class MyCircularQueue {

    private int front; // 指向队头元素
    private int rear; // 指向队尾元素的下一个元素
    private int capacity; //声明数组容量
    private int[] array; // 使用数组实现循环队列

    /** Initialize your data structure here. Set the size of the queue to be k. */
    public MyCircularQueue(int k) {
        front = 0;
        rear = 0;
        capacity = k + 1;
        array = new int[capacity];
    }

    /** Insert an element into the circular queue. Return true if the operation is successful. */
    public boolean enQueue(int value) {
        if(isFull()) return false;
        array[rear] = value;
        rear = (rear + 1) % capacity;
        return true;
    }

    /** Delete an element from the circular queue. Return true if the operation is successful. */
    public boolean deQueue() {
        if(isEmpty()) return false;
        front = (front + 1) % capacity;
        return true;
    }

    /** Get the front item from the queue. */
    public int Front() {
        if(isEmpty()) return -1;
        return array[front];
    }

    /** Get the last item from the queue. */
    public int Rear() {
        if(isEmpty()) return -1;
        return array[(rear - 1 + capacity) % capacity];
    }

    /** Checks whether the circular queue is empty or not. */
    public boolean isEmpty() {
        return front == rear;
    }

    /** Checks whether the circular queue is full or not. */
    public boolean isFull() {
        // 为了避免 “队列为空” 和 “队列为满” 的判别条件冲突,有意浪费一个元素空间
        // 即当 rear 循环到数组的前面,要从后面追上 front,还差一格的时判定为队列为满
        return (rear + 1) % capacity == front; 
    }
}

/**
 * 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();
 */

Python

'''
Author: Goog Tech
Date: 2020-09-07 08:16:08
LastEditTime: 2020-09-07 08:17:10
Description: https://leetcode-cn.com/problems/design-circular-queue/
FilePath: \leetcode-googtech\#622. Design Circular Queue\Solution.py
WebSite: https://algorithm.show/
'''

class MyCircularQueue(object):

    def __init__(self, k):
        """
        Initialize your data structure here. Set the size of the queue to be k.
        :type k: int
        """
        self.front = 0 # 指向队头元素
        self.rear = 0 # 指向队尾元素的下一个元素
        self.capacity = k + 1 # 声明数组容量
        self.array = [0 for _ in range(self.capacity)] # 使用数组实现循环队列

    def enQueue(self, value):
        """
        Insert an element into the circular queue. Return true if the operation is successful.
        :type value: int
        :rtype: bool
        """
        if self.isFull(): return False
        self.array[self.rear] = value
        self.rear = (self.rear + 1) % self.capacity;
        return True;

    def deQueue(self):
        """
        Delete an element from the circular queue. Return true if the operation is successful.
        :rtype: bool
        """
        if self.isEmpty(): return False
        self.front = (self.front + 1) % self.capacity
        return True

    def Front(self):
        """
        Get the front item from the queue.
        :rtype: int
        """
        if self.isEmpty(): return -1
        return self.array[self.front]

    def Rear(self):
        """
        Get the last item from the queue.
        :rtype: int
        """
        if self.isEmpty(): return -1
        return self.array[(self.rear - 1 + self.capacity) % self.capacity]

    def isEmpty(self):
        """
        Checks whether the circular queue is empty or not.
        :rtype: bool
        """
        return self.front == self.rear

    def isFull(self):
        """
        Checks whether the circular queue is full or not.
        :rtype: bool
        """
        # 为了避免 “队列为空” 和 “队列未满” 的判别条件冲突,有意浪费一个元素空间
        # 即当 rear 循环到数组的前面,要从后面追上 front,还差一格的时候判定为队列为满
        return (self.rear + 1) % self.capacity == self.front

# Your MyCircularQueue object will be instantiated and called as such:
# obj = MyCircularQueue(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()