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中等
设计
队列
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622. 设计循环队列

English Version

题目描述

设计你的循环队列实现。 循环队列是一种线性数据结构，其操作表现基于 FIFO（先进先出）原则并且队尾被连接在队首之后以形成一个循环。它也被称为“环形缓冲器”。

循环队列的一个好处是我们可以利用这个队列之前用过的空间。在一个普通队列里，一旦一个队列满了，我们就不能插入下一个元素，即使在队列前面仍有空间。但是使用循环队列，我们能使用这些空间去存储新的值。

你的实现应该支持如下操作：

  • MyCircularQueue(k): 构造器，设置队列长度为 k 。
  • Front: 从队首获取元素。如果队列为空，返回 -1 。
  • Rear: 获取队尾元素。如果队列为空，返回 -1 。
  • enQueue(value): 向循环队列插入一个元素。如果成功插入则返回真。
  • deQueue(): 从循环队列中删除一个元素。如果成功删除则返回真。
  • isEmpty(): 检查循环队列是否为空。
  • isFull(): 检查循环队列是否已满。

 

示例：

MyCircularQueue circularQueue = new MyCircularQueue(3); // 设置长度为 3
circularQueue.enQueue(1);  // 返回 true
circularQueue.enQueue(2);  // 返回 true
circularQueue.enQueue(3);  // 返回 true
circularQueue.enQueue(4);  // 返回 false，队列已满
circularQueue.Rear();  // 返回 3
circularQueue.isFull();  // 返回 true
circularQueue.deQueue();  // 返回 true
circularQueue.enQueue(4);  // 返回 true
circularQueue.Rear();  // 返回 4

 

提示：

  • 所有的值都在 0 至 1000 的范围内；
  • 操作数将在 1 至 1000 的范围内；
  • 请不要使用内置的队列库。

解法

方法一

Python3

class MyCircularQueue:
    def __init__(self, k: int):
        self.q = [0] * k
        self.front = 0
        self.size = 0
        self.capacity = k

    def enQueue(self, value: int) -> bool:
        if self.isFull():
            return False
        idx = (self.front + self.size) % self.capacity
        self.q[idx] = value
        self.size += 1
        return True

    def deQueue(self) -> bool:
        if self.isEmpty():
            return False
        self.front = (self.front + 1) % self.capacity
        self.size -= 1
        return True

    def Front(self) -> int:
        return -1 if self.isEmpty() else self.q[self.front]

    def Rear(self) -> int:
        if self.isEmpty():
            return -1
        idx = (self.front + self.size - 1) % self.capacity
        return self.q[idx]

    def isEmpty(self) -> bool:
        return self.size == 0

    def isFull(self) -> bool:
        return self.size == self.capacity


# 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()

Java

class MyCircularQueue {
    private int[] q;
    private int front;
    private int size;
    private int capacity;

    public MyCircularQueue(int k) {
        q = new int[k];
        capacity = k;
    }

    public boolean enQueue(int value) {
        if (isFull()) {
            return false;
        }
        int idx = (front + size) % capacity;
        q[idx] = value;
        ++size;
        return true;
    }

    public boolean deQueue() {
        if (isEmpty()) {
            return false;
        }
        front = (front + 1) % capacity;
        --size;
        return true;
    }

    public int Front() {
        if (isEmpty()) {
            return -1;
        }
        return q[front];
    }

    public int Rear() {
        if (isEmpty()) {
            return -1;
        }
        int idx = (front + size - 1) % capacity;
        return q[idx];
    }

    public boolean isEmpty() {
        return size == 0;
    }

    public boolean isFull() {
        return size == capacity;
    }
}

/**
 * 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();
 */

C++

class MyCircularQueue {
private:
    int front;
    int size;
    int capacity;
    vector<int> q;

public:
    MyCircularQueue(int k) {
        capacity = k;
        q = vector<int>(k);
        front = size = 0;
    }

    bool enQueue(int value) {
        if (isFull()) return false;
        int idx = (front + size) % capacity;
        q[idx] = value;
        ++size;
        return true;
    }

    bool deQueue() {
        if (isEmpty()) return false;
        front = (front + 1) % capacity;
        --size;
        return true;
    }

    int Front() {
        if (isEmpty()) return -1;
        return q[front];
    }

    int Rear() {
        if (isEmpty()) return -1;
        int idx = (front + size - 1) % capacity;
        return q[idx];
    }

    bool isEmpty() {
        return size == 0;
    }

    bool isFull() {
        return size == capacity;
    }
};

/**
 * Your MyCircularQueue object will be instantiated and called as such:
 * MyCircularQueue* obj = new MyCircularQueue(k);
 * bool param_1 = obj->enQueue(value);
 * bool param_2 = obj->deQueue();
 * int param_3 = obj->Front();
 * int param_4 = obj->Rear();
 * bool param_5 = obj->isEmpty();
 * bool param_6 = obj->isFull();
 */

Go

type MyCircularQueue struct {
	front    int
	size     int
	capacity int
	q        []int
}

func Constructor(k int) MyCircularQueue {
	q := make([]int, k)
	return MyCircularQueue{0, 0, k, q}
}

func (this *MyCircularQueue) EnQueue(value int) bool {
	if this.IsFull() {
		return false
	}
	idx := (this.front + this.size) % this.capacity
	this.q[idx] = value
	this.size++
	return true
}

func (this *MyCircularQueue) DeQueue() bool {
	if this.IsEmpty() {
		return false
	}
	this.front = (this.front + 1) % this.capacity
	this.size--
	return true
}

func (this *MyCircularQueue) Front() int {
	if this.IsEmpty() {
		return -1
	}
	return this.q[this.front]
}

func (this *MyCircularQueue) Rear() int {
	if this.IsEmpty() {
		return -1
	}
	idx := (this.front + this.size - 1) % this.capacity
	return this.q[idx]
}

func (this *MyCircularQueue) IsEmpty() bool {
	return this.size == 0
}

func (this *MyCircularQueue) IsFull() bool {
	return this.size == this.capacity
}

/**
 * Your MyCircularQueue object will be instantiated and called as such:
 * obj := Constructor(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();
 */

TypeScript

class MyCircularQueue {
    private queue: number[];
    private left: number;
    private right: number;
    private capacity: number;

    constructor(k: number) {
        this.queue = new Array(k);
        this.left = 0;
        this.right = 0;
        this.capacity = k;
    }

    enQueue(value: number): boolean {
        if (this.isFull()) {
            return false;
        }
        this.queue[this.right % this.capacity] = value;
        this.right++;
        return true;
    }

    deQueue(): boolean {
        if (this.isEmpty()) {
            return false;
        }
        this.left++;
        return true;
    }

    Front(): number {
        if (this.isEmpty()) {
            return -1;
        }
        return this.queue[this.left % this.capacity];
    }

    Rear(): number {
        if (this.isEmpty()) {
            return -1;
        }
        return this.queue[(this.right - 1) % this.capacity];
    }

    isEmpty(): boolean {
        return this.right - this.left === 0;
    }

    isFull(): boolean {
        return this.right - this.left === this.capacity;
    }
}

/**
 * Your MyCircularQueue object will be instantiated and called as such:
 * var obj = new MyCircularQueue(k)
 * var param_1 = obj.enQueue(value)
 * var param_2 = obj.deQueue()
 * var param_3 = obj.Front()
 * var param_4 = obj.Rear()
 * var param_5 = obj.isEmpty()
 * var param_6 = obj.isFull()
 */

Rust

struct MyCircularQueue {
    queue: Vec<i32>,
    left: usize,
    right: usize,
    capacity: usize,
}

/**
 * `&self` means the method takes an immutable reference.
 * If you need a mutable reference, change it to `&mut self` instead.
 */
impl MyCircularQueue {
    fn new(k: i32) -> Self {
        let k = k as usize;
        Self {
            queue: vec![0; k],
            left: 0,
            right: 0,
            capacity: k,
        }
    }

    fn en_queue(&mut self, value: i32) -> bool {
        if self.is_full() {
            return false;
        }
        self.queue[self.right % self.capacity] = value;
        self.right += 1;
        true
    }

    fn de_queue(&mut self) -> bool {
        if self.is_empty() {
            return false;
        }
        self.left += 1;
        true
    }

    fn front(&self) -> i32 {
        if self.is_empty() {
            return -1;
        }
        self.queue[self.left % self.capacity]
    }

    fn rear(&self) -> i32 {
        if self.is_empty() {
            return -1;
        }
        self.queue[(self.right - 1) % self.capacity]
    }

    fn is_empty(&self) -> bool {
        self.right - self.left == 0
    }

    fn is_full(&self) -> bool {
        self.right - self.left == self.capacity
    }
}