[Leet Code] 622. Design Circular Queue

Design Circular Queue

 

 문제 설명

 

Design 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 be k.
• 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. Return true if the operation is successful.
• boolean deQueue() Deletes an element from the circular queue. Return true 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. 

 

 제한 사항

 

• 1 <= k <= 1000
• 0 <= value <= 1000
• At most 3000 calls will be made to enQueue, deQueue, Front, Rear, isEmpty, and isFull.

 

 입출력 예

 

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

 

 Python 코드

 

Python code 

class MyCirculurQueue:
    def __init__(self, k):
        self.q = [None] * k
        self.maxlen = k
        self.p1 = 0
        self.p2 = 0
 
    # enQueue(): rear 포인터 이동
    def enQueue(self, value):
        if self.q[self.p2] is None:
            self.q[self.p2] = value
            self.p2 = (self.p2 + 1) % self.maxlen
            return True
        else:
            return False
 
    # deQueue(): front 포인터 이동
    def deQueue(self):
        if self.q[self.p1] is None:
            return False
        else:
            self.q[self.p1] = None
            self.p1 = (self.p1 + 1) % self.maxlen
            return True
 
    def Front(self):
        return -1 if self.q[self.p1] is None else self.q[self.p1]
 
    def Rear(self):
        return -1 if self.q[self.p2 - 1] is None else self.q[self.p2 - 1]
 
    def isEmpty(self):
        return self.p1 == self.p2 and self.q[self.p1] is None
 
    def isFull(self):
        return self.p1 == self.p2 and self.q[self.p1] is not None

* 참고 링크 : https://deep-learning-study.tistory.com/480

 

 C++ 코드

 

C ++ code

 
class MyCircularQueue {
public:
  MyCircularQueue(int k): q_(k) {}
  
  bool enQueue(int value) {
    if (isFull()) return false;
    q_[(head_ + size_) % q_.size()] = value;    
    ++size_;
    return true;
  }
  
  bool deQueue() {
    if (isEmpty()) return false;
    head_ = (head_ + 1) % q_.size();
    --size_;
    return true;
  }
 
  int Front() { return isEmpty() ? -1 : q_[head_]; }
 
  int Rear() { return isEmpty() ? -1 : q_[(head_ + size_ - 1) % q_.size()]; }
 
  bool isEmpty() { return size_ == 0; }
 
  bool isFull() { return size_ == q_.size(); }
private:
  vector<int> q_;
  int head_ = 0;
  int size_ = 0;
};

* 참고 링크 : https://zxi.mytechroad.com/blog/desgin/leetcode-622-design-circular-queue/

 

 출처

 

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