[LeetCode] 874. Design Circular Deque

题目描述

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 32
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 [1, 1000].
The number of operations will be in the range of [1, 1000].
Please do not use the built-in Deque library.
题目要求实现一个循环双端队列，我们可以使用std::list (std::list 底层是双向链表，std::forward_list是stl中的单向链表)实现，或者自己新建一个双向链表。

C++ 实现

class MyCircularDeque {
public:
    /** Initialize your data structure here. Set the size of the deque to be k. */
    MyCircularDeque(int k) {
        upper_size = k;
    }

    /** Adds an item at the front of Deque. Return true if the operation is successful. */
    bool insertFront(int value) {
        if(deque.size() < upper_size)
        {
            deque.emplace_front(value);
            return true;
        }
        return false;
    }

    /** Adds an item at the rear of Deque. Return true if the operation is successful. */
    bool insertLast(int value) {
        if (deque.size() < upper_size)
        {
            deque.emplace_back(value);
            return true;
        }
        return false;
    }

    /** Deletes an item from the front of Deque. Return true if the operation is successful. */
    bool deleteFront() {
        if (!deque.empty())
        {
            deque.pop_front();
            return true;
        }
        return false;
    }

    /** Deletes an item from the rear of Deque. Return true if the operation is successful. */
    bool deleteLast() {
        if (!deque.empty())
        {
            deque.pop_back();
            return true;
        }
        return false;
    }

    /** Get the front item from the deque. */
    int getFront() {
        if (deque.empty())
        {
            return -1;
        }
        return deque.front();
    }

    /** Get the last item from the deque. */
    int getRear() {
        if (deque.empty())
        {
            return -1;
        }
        return deque.back();
    }

    /** Checks whether the circular deque is empty or not. */
    bool isEmpty() {
        return deque.empty();
    }

    /** Checks whether the circular deque is full or not. */
    bool isFull() {
        return deque.size() == upper_size;
    }
private:
    list<int> deque;
    int upper_size;
};

/**
 * 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();
 */