[LeetCode] 641.Design Circular Deque 设计环形双向队列

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

Your implementation should support following operations:

MyCircularDeque(k): Constructor, set the size of the deque to be k.
insertFront(): Adds an item at the front of Deque. Return true if the operation is successful.
insertLast(): Adds an item at the rear of Deque. Return true if the operation is successful.
deleteFront(): Deletes an item from the front of Deque. Return true if the operation is successful.
deleteLast(): Deletes an item from the rear of Deque. Return true if the operation is successful.
getFront(): Gets the front item from the Deque. If the deque is empty, return -1.
getRear(): Gets the last item from Deque. If the deque is empty, return -1.
isEmpty(): Checks whether Deque is empty or not.
isFull(): Checks whether Deque is full or not.

Example:

MyCircularDeque circularDeque = new MycircularDeque(3); // set the size to be 3
circularDeque.insertLast(1); // return true
circularDeque.insertLast(2); // return true
circularDeque.insertFront(3); // return true
circularDeque.insertFront(4); // return false, the queue is full
circularDeque.getRear(); // return 2
circularDeque.isFull(); // return true
circularDeque.deleteLast(); // return true
circularDeque.insertFront(4); // return true
circularDeque.getFront(); // return 4

Note:

All values will be in the range of [0, 1000].
The number of operations will be in the range of [1, 1000].
Please do not use the built-in Deque library. 

622.Design Circular Queue 的拓展。

解法：doubly Linked List

Java:

class MyCircularDeque {
    int size;
    int k;
    DoubleListNode head;
    DoubleListNode tail;
    /** Initialize your data structure here. Set the size of the deque to be k. */
    public MyCircularDeque(int k) {
        head = new DoubleListNode(-1);
        tail = new DoubleListNode(-1);
        head.pre = tail;
        tail.next = head;
        this.k = k;
        this.size = 0;
    }
    
    /** Adds an item at the front of Deque. Return true if the operation is successful. */
    public boolean insertFront(int value) {
        if (size == k)
            return false;
        DoubleListNode node = new DoubleListNode(value);
        node.next = head;
        node.pre = head.pre;
        head.pre.next = node;
        head.pre = node;
        size++;
        return true;
    }
    
    /** Adds an item at the rear of Deque. Return true if the operation is successful. */
    public boolean insertLast(int value) {
        if (size == k)
            return false;
        DoubleListNode node = new DoubleListNode(value);
        node.next = tail.next;
        tail.next.pre = node;
        tail.next = node;
        node.pre = tail;
        size++;
        return true;
    }
    
    /** Deletes an item from the front of Deque. Return true if the operation is successful. */
    public boolean deleteFront() {
        if (size == 0)
            return false;
        head.pre.pre.next = head;
        head.pre = head.pre.pre;
        size--;
        return true;
    }
    
    /** Deletes an item from the rear of Deque. Return true if the operation is successful. */
    public boolean deleteLast() {
        if (size == 0)
            return false;
        tail.next.next.pre = tail;
        tail.next = tail.next.next;
        size--;
        return true;
    }
    
    /** Get the front item from the deque. */
    public int getFront() {
        return head.pre.val;
    }
    
    /** Get the last item from the deque. */
    public int getRear() {
        return tail.next.val;
    }
    
    /** 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 == k;
    }
}

class DoubleListNode {
    DoubleListNode pre;
    DoubleListNode next;
    int val;
    public DoubleListNode(int val) {
        this.val = val;
    }
}

Python:

class Node:
    def __init__(self, value):
        self.val = value
        self.next = self.pre = None
        
class MyCircularDeque:

    def __init__(self, k):
        self.head = self.tail = Node(-1)
        self.head.next = self.tail
        self.tail.pre = self.head
        self.size = k
        self.curSize = 0

    def add(self, value, preNode):
        new = Node(value)
        new.pre = preNode
        new.next = preNode.next
        new.pre.next = new.next.pre = new
        self.curSize += 1
        
    def remove(self, preNode):
        node = preNode.next
        node.pre.next = node.next
        node.next.pre = node.pre
        self.curSize -= 1
    
    def insertFront(self, value):
        if self.curSize < self.size:
            self.add(value, self.head)
            return True
        return False

    def insertLast(self, value):
        if self.curSize < self.size:
            self.add(value, self.tail.pre)
            return True
        return False

    def deleteFront(self):
        if self.curSize:
            self.remove(self.head)
            return True
        return False

    def deleteLast(self):
        if self.curSize:
            self.remove(self.tail.pre.pre)
            return True
        return False

    def getFront(self):
        if self.curSize:
            return self.head.next.val
        return -1

    def getRear(self):
        if self.curSize:
            return self.tail.pre.val
        return -1

    def isEmpty(self):
        return self.curSize == 0

    def isFull(self):
        return self.curSize == self.size

C++:　　

#include <vector>
#include <iostream>

using namespace std;

class MyCircularDeque {
private:
    vector<int> buffer;
    int cnt;
    int k;
    int front;
    int rear;
public:
    /** Initialize your data structure here. Set the size of the deque to be k. */
    MyCircularDeque(int k): buffer(k, 0), cnt(0), k(k), front(k - 1), rear(0) {
    }
    
    /** Adds an item at the front of Deque. Return true if the operation is successful. */
    bool insertFront(int value) {
        if (cnt == k) {
            return false;
        }
        buffer[front] = value;
        front = (front - 1 + k) % k;
        ++cnt;

        return true;
    }
    
    /** Adds an item at the rear of Deque. Return true if the operation is successful. */
    bool insertLast(int value) {
        if (cnt == k) {
            return false;
        }
        buffer[rear] = value;
        rear = (rear + 1) % k;
        ++cnt;

        return true;
    }
    
    /** Deletes an item from the front of Deque. Return true if the operation is successful. */
    bool deleteFront() {
        if (cnt == 0) {
            return false;
        }
        front = (front + 1) % k;
        --cnt;

        return true;
    }
    
    /** Deletes an item from the rear of Deque. Return true if the operation is successful. */
    bool deleteLast() {
        if (cnt == 0) {
            return false;
        }
        rear = (rear - 1 + k) % k;
        --cnt;

        return true;
    }
    
    /** Get the front item from the deque. */
    int getFront() {
        if (cnt == 0) {
            return -1;
        }
        return buffer[(front + 1) % k];
    }
    
    /** Get the last item from the deque. */
    int getRear() {
        if (cnt == 0) {
            return -1;
        }
        return buffer[(rear - 1 + k) % k];
    }
    
    /** Checks whether the circular deque is empty or not. */
    bool isEmpty() {
        return cnt == 0;
    }
    
    /** Checks whether the circular deque is full or not. */
    bool isFull() {
        return cnt == k;
    }
};

/**
 * 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();
 */

#if DEBUG
int main(int argc, char** argv) {
    return 0;
}
#endif

　　

　　

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