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641. Design Circular Deque

Description

Design your implementation of the circular double-ended queue (deque).

Implement the MyCircularDeque class:

  • MyCircularDeque(int k) Initializes the deque with a maximum size of k.
  • boolean insertFront() Adds an item at the front of Deque. Returns true if the operation is successful, or false otherwise.
  • boolean insertLast() Adds an item at the rear of Deque. Returns true if the operation is successful, or false otherwise.
  • boolean deleteFront() Deletes an item from the front of Deque. Returns true if the operation is successful, or false otherwise.
  • boolean deleteLast() Deletes an item from the rear of Deque. Returns true if the operation is successful, or false otherwise.
  • int getFront() Returns the front item from the Deque. Returns -1 if the deque is empty.
  • int getRear() Returns the last item from Deque. Returns -1 if the deque is empty.
  • boolean isEmpty() Returns true if the deque is empty, or false otherwise.
  • boolean isFull() Returns true if the deque is full, or false otherwise.

Β 

Example 1:

Input
["MyCircularDeque", "insertLast", "insertLast", "insertFront", "insertFront", "getRear", "isFull", "deleteLast", "insertFront", "getFront"]
[[3], [1], [2], [3], [4], [], [], [], [4], []]
Output
[null, true, true, true, false, 2, true, true, true, 4]

Explanation
MyCircularDeque myCircularDeque = new MyCircularDeque(3);
myCircularDeque.insertLast(1);  // return True
myCircularDeque.insertLast(2);  // return True
myCircularDeque.insertFront(3); // return True
myCircularDeque.insertFront(4); // return False, the queue is full.
myCircularDeque.getRear();      // return 2
myCircularDeque.isFull();       // return True
myCircularDeque.deleteLast();   // return True
myCircularDeque.insertFront(4); // return True
myCircularDeque.getFront();     // return 4

Β 

Constraints:

  • 1 <= k <= 1000
  • 0 <= value <= 1000
  • At most 2000 calls will be made to insertFront, insertLast, deleteFront, deleteLast, getFront, getRear, isEmpty, isFull.

Solutions

Solution 1: Array

We can use an array to implement the circular deque. We maintain a pointer \(\textit{front}\) pointing to the front of the queue, a variable \(\textit{size}\) representing the number of elements in the queue, and a variable \(\textit{capacity}\) representing the queue's capacity. We use an array \(\textit{q}\) to store the elements.

When \(\textit{insertFront}\) is called, we first check if the queue is full; if so, return \(\text{false}\). Otherwise, we move \(\textit{front}\) one position forward (using modular arithmetic for circular wrapping), insert the new element at \(\textit{front}\), and increment \(\textit{size}\) by 1.

When \(\textit{insertLast}\) is called, we first check if the queue is full; if so, return \(\text{false}\). Otherwise, we compute the insertion position (using \(\textit{front}\) and \(\textit{size}\)), insert the new element there, and increment \(\textit{size}\) by 1.

When \(\textit{deleteFront}\) is called, we first check if the queue is empty; if so, return \(\text{false}\). Otherwise, we move \(\textit{front}\) one position backward (using modular arithmetic for circular wrapping) and decrement \(\textit{size}\) by 1.

When \(\textit{deleteLast}\) is called, we first check if the queue is empty; if so, return \(\text{false}\). Otherwise, we decrement \(\textit{size}\) by 1.

When \(\textit{getFront}\) is called, we first check if the queue is empty; if so, return \(-1\). Otherwise, we return \(\textit{q}[\textit{front}]\).

When \(\textit{getRear}\) is called, we first check if the queue is empty; if so, return \(-1\). Otherwise, we compute the position of the rear element (using \(\textit{front}\) and \(\textit{size}\)) and return the element at that position.

When \(\textit{isEmpty}\) is called, we check whether \(\textit{size}\) equals \(0\).

When \(\textit{isFull}\) is called, we check whether \(\textit{size}\) equals \(\textit{capacity}\).

All operations above have a time complexity of \(O(1)\) and a space complexity of \(O(k)\), where \(k\) is the capacity of the deque.

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class MyCircularDeque:
    def __init__(self, k: int):
        """
        Initialize your data structure here. Set the size of the deque to be k.
        """
        self.q = [0] * k
        self.front = 0
        self.size = 0
        self.capacity = k

    def insertFront(self, value: int) -> bool:
        """
        Adds an item at the front of Deque. Return true if the operation is successful.
        """
        if self.isFull():
            return False
        if not self.isEmpty():
            self.front = (self.front - 1 + self.capacity) % self.capacity
        self.q[self.front] = value
        self.size += 1
        return True

    def insertLast(self, value: int) -> bool:
        """
        Adds an item at the rear of Deque. Return true if the operation is successful.
        """
        if self.isFull():
            return False
        idx = (self.front + self.size) % self.capacity
        self.q[idx] = value
        self.size += 1
        return True

    def deleteFront(self) -> bool:
        """
        Deletes an item from the front of Deque. Return true if the operation is successful.
        """
        if self.isEmpty():
            return False
        self.front = (self.front + 1) % self.capacity
        self.size -= 1
        return True

    def deleteLast(self) -> bool:
        """
        Deletes an item from the rear of Deque. Return true if the operation is successful.
        """
        if self.isEmpty():
            return False
        self.size -= 1
        return True

    def getFront(self) -> int:
        """
        Get the front item from the deque.
        """
        if self.isEmpty():
            return -1
        return self.q[self.front]

    def getRear(self) -> int:
        """
        Get the last item from the deque.
        """
        if self.isEmpty():
            return -1
        idx = (self.front + self.size - 1) % self.capacity
        return self.q[idx]

    def isEmpty(self) -> bool:
        """
        Checks whether the circular deque is empty or not.
        """
        return self.size == 0

    def isFull(self) -> bool:
        """
        Checks whether the circular deque is full or not.
        """
        return self.size == self.capacity


# Your MyCircularDeque object will be instantiated and called as such:
# obj = MyCircularDeque(k)
# param_1 = obj.insertFront(value)
# param_2 = obj.insertLast(value)
# param_3 = obj.deleteFront()
# param_4 = obj.deleteLast()
# param_5 = obj.getFront()
# param_6 = obj.getRear()
# param_7 = obj.isEmpty()
# param_8 = obj.isFull()

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

    /** Initialize your data structure here. Set the size of the deque to be k. */
    public MyCircularDeque(int k) {
        q = new int[k];
        capacity = k;
    }

    /** Adds an item at the front of Deque. Return true if the operation is successful. */
    public boolean insertFront(int value) {
        if (isFull()) {
            return false;
        }
        if (!isEmpty()) {
            front = (front - 1 + capacity) % capacity;
        }
        q[front] = value;
        ++size;
        return true;
    }

    /** Adds an item at the rear of Deque. Return true if the operation is successful. */
    public boolean insertLast(int value) {
        if (isFull()) {
            return false;
        }
        int idx = (front + size) % capacity;
        q[idx] = value;
        ++size;
        return true;
    }

    /** Deletes an item from the front of Deque. Return true if the operation is successful. */
    public boolean deleteFront() {
        if (isEmpty()) {
            return false;
        }
        front = (front + 1) % capacity;
        --size;
        return true;
    }

    /** Deletes an item from the rear of Deque. Return true if the operation is successful. */
    public boolean deleteLast() {
        if (isEmpty()) {
            return false;
        }
        --size;
        return true;
    }

    /** Get the front item from the deque. */
    public int getFront() {
        if (isEmpty()) {
            return -1;
        }
        return q[front];
    }

    /** Get the last item from the deque. */
    public int getRear() {
        if (isEmpty()) {
            return -1;
        }
        int idx = (front + size - 1) % capacity;
        return q[idx];
    }

    /** Checks whether the circular deque is empty or not. */
    public boolean isEmpty() {
        return size == 0;
    }

    /** Checks whether the circular deque is full or not. */
    public boolean isFull() {
        return size == capacity;
    }
}

/**
 * Your MyCircularDeque object will be instantiated and called as such:
 * MyCircularDeque obj = new MyCircularDeque(k);
 * boolean param_1 = obj.insertFront(value);
 * boolean param_2 = obj.insertLast(value);
 * boolean param_3 = obj.deleteFront();
 * boolean param_4 = obj.deleteLast();
 * int param_5 = obj.getFront();
 * int param_6 = obj.getRear();
 * boolean param_7 = obj.isEmpty();
 * boolean param_8 = obj.isFull();
 */

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class MyCircularDeque {
public:
    vector<int> q;
    int front = 0;
    int size = 0;
    int capacity = 0;

    MyCircularDeque(int k) {
        q.assign(k, 0);
        capacity = k;
    }

    bool insertFront(int value) {
        if (isFull()) {
            return false;
        }
        if (!isEmpty()) {
            front = (front - 1 + capacity) % capacity;
        }
        q[front] = value;
        ++size;
        return true;
    }

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

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

    bool deleteLast() {
        if (isEmpty()) {
            return false;
        }
        --size;
        return true;
    }

    int getFront() {
        return isEmpty() ? -1 : q[front];
    }

    int getRear() {
        return isEmpty() ? -1 : q[(front + size - 1) % capacity];
    }

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

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

/**
 * Your MyCircularDeque object will be instantiated and called as such:
 * MyCircularDeque* obj = new MyCircularDeque(k);
 * bool param_1 = obj->insertFront(value);
 * bool param_2 = obj->insertLast(value);
 * bool param_3 = obj->deleteFront();
 * bool param_4 = obj->deleteLast();
 * int param_5 = obj->getFront();
 * int param_6 = obj->getRear();
 * bool param_7 = obj->isEmpty();
 * bool param_8 = obj->isFull();
 */

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

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

func (this *MyCircularDeque) InsertFront(value int) bool {
    if this.IsFull() {
        return false
    }
    if !this.IsEmpty() {
        this.front = (this.front - 1 + this.capacity) % this.capacity
    }
    this.q[this.front] = value
    this.size++
    return true
}

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

func (this *MyCircularDeque) DeleteLast() bool {
    if this.IsEmpty() {
        return false
    }
    this.size -= 1
    return true
}

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

func (this *MyCircularDeque) GetRear() int {
    if this.IsEmpty() {
        return -1
    }
    return this.q[(this.front+this.size-1)%this.capacity]
}

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

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

/**
 * Your MyCircularDeque object will be instantiated and called as such:
 * obj := Constructor(k);
 * param_1 := obj.InsertFront(value);
 * param_2 := obj.InsertLast(value);
 * param_3 := obj.DeleteFront();
 * param_4 := obj.DeleteLast();
 * param_5 := obj.GetFront();
 * param_6 := obj.GetRear();
 * param_7 := obj.IsEmpty();
 * param_8 := obj.IsFull();
 */

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class MyCircularDeque {
    private vals: number[];
    private length: number;
    private size: number;
    private start: number;
    private end: number;

    constructor(k: number) {
        this.vals = new Array(k).fill(0);
        this.start = 0;
        this.end = 0;
        this.length = 0;
        this.size = k;
    }

    insertFront(value: number): boolean {
        if (this.isFull()) {
            return false;
        }

        if (this.start === 0) {
            this.start = this.size - 1;
        } else {
            this.start--;
        }
        this.vals[this.start] = value;
        this.length++;
        return true;
    }

    insertLast(value: number): boolean {
        if (this.isFull()) {
            return false;
        }

        this.vals[this.end] = value;
        this.length++;
        if (this.end + 1 === this.size) {
            this.end = 0;
        } else {
            this.end++;
        }
        return true;
    }

    deleteFront(): boolean {
        if (this.isEmpty()) {
            return false;
        }

        if (this.start + 1 === this.size) {
            this.start = 0;
        } else {
            this.start++;
        }
        this.length--;
        return true;
    }

    deleteLast(): boolean {
        if (this.isEmpty()) {
            return false;
        }

        if (this.end === 0) {
            this.end = this.size - 1;
        } else {
            this.end--;
        }
        this.length--;
        return true;
    }

    getFront(): number {
        if (this.isEmpty()) {
            return -1;
        }

        return this.vals[this.start];
    }

    getRear(): number {
        if (this.isEmpty()) {
            return -1;
        }

        if (this.end === 0) {
            return this.vals[this.size - 1];
        }
        return this.vals[this.end - 1];
    }

    isEmpty(): boolean {
        return this.length === 0;
    }

    isFull(): boolean {
        return this.length === this.size;
    }
}

/**
 * Your MyCircularDeque object will be instantiated and called as such:
 * var obj = new MyCircularDeque(k)
 * var param_1 = obj.insertFront(value)
 * var param_2 = obj.insertLast(value)
 * var param_3 = obj.deleteFront()
 * var param_4 = obj.deleteLast()
 * var param_5 = obj.getFront()
 * var param_6 = obj.getRear()
 * var param_7 = obj.isEmpty()
 * var param_8 = obj.isFull()
 */

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