/**
 * File: array_deque.cs
 * Created Time: 2023-03-08
 * Author: hpstory (hpstory1024@163.com)
 */

using NUnit.Framework;

namespace hello_algo.chapter_stack_and_queue
{
    /* 基于环形数组实现的双向队列 */
    public class ArrayDeque
    {
        private readonly int[] nums;  // 用于存储双向队列元素的数组
        private int front;   // 队首指针，指向队首元素
        private int queSize; // 双向队列长度

        /* 构造方法 */
        public ArrayDeque(int capacity)
        {
            this.nums = new int[capacity];
            front = queSize = 0;
        }

        /* 获取双向队列的容量 */
        public int capacity()
        {
            return nums.Length;
        }

        /* 获取双向队列的长度 */
        public int size()
        {
            return queSize;
        }

        /* 判断双向队列是否为空 */
        public bool isEmpty()
        {
            return queSize == 0;
        }

        /* 计算环形数组索引 */
        private int index(int i)
        {
            // 通过取余操作实现数组首尾相连
            // 当 i 越过数组尾部后，回到头部
            // 当 i 越过数组头部后，回到尾部
            return (i + capacity()) % capacity();
        }

        /* 队首入队 */
        public void pushFirst(int num)
        {
            if (queSize == capacity())
            {
                Console.WriteLine("双向队列已满");
                return;
            }
            // 队首指针向左移动一位
            // 通过取余操作，实现 front 越过数组头部后回到尾部
            front = index(front - 1);
            // 将 num 添加至队首
            nums[front] = num;
            queSize++;
        }

        /* 队尾入队 */
        public void pushLast(int num)
        {
            if (queSize == capacity())
            {
                Console.WriteLine("双向队列已满");
                return;
            }
            // 计算尾指针，指向队尾索引 + 1
            int rear = index(front + queSize);
            // 将 num 添加至队尾
            nums[rear] = num;
            queSize++;
        }

        /* 队首出队 */
        public int pollFirst()
        {
            int num = peekFirst();
            // 队首指针向后移动一位
            front = index(front + 1);
            queSize--;
            return num;
        }

        /* 队尾出队 */
        public int pollLast()
        {
            int num = peekLast();
            queSize--;
            return num;
        }

        /* 访问队首元素 */
        public int peekFirst()
        {
            if (isEmpty())
            {
                throw new InvalidOperationException();
            }              
            return nums[front];
        }

        /* 访问队尾元素 */
        public int peekLast()
        {
            if (isEmpty())
            {
                throw new InvalidOperationException();
            }               
            // 计算尾元素索引
            int last = index(front + queSize - 1);
            return nums[last];
        }

        /* 返回数组用于打印 */
        public int[] toArray()
        {
            // 仅转换有效长度范围内的列表元素
            int[] res = new int[queSize];
            for (int i = 0, j = front; i < queSize; i++, j++)
            {
                res[i] = nums[index(j)];
            }
            return res;
        }
    }

    public class array_deque
    {
        [Test]
        public void Test()
        {
            /* 初始化双向队列 */
            ArrayDeque deque = new ArrayDeque(10);
            deque.pushLast(3);
            deque.pushLast(2);
            deque.pushLast(5);
            Console.WriteLine("双向队列 deque = " + string.Join(" ", deque.toArray()));

            /* 访问元素 */
            int peekFirst = deque.peekFirst();
            Console.WriteLine("队首元素 peekFirst = " + peekFirst);
            int peekLast = deque.peekLast();
            Console.WriteLine("队尾元素 peekLast = " + peekLast);

            /* 元素入队 */
            deque.pushLast(4);
            Console.WriteLine("元素 4 队尾入队后 deque = " + string.Join(" ", deque.toArray()));
            deque.pushFirst(1);
            Console.WriteLine("元素 1 队首入队后 deque = " + string.Join(" ", deque.toArray()));

            /* 元素出队 */
            int pollLast = deque.pollLast();
            Console.WriteLine("队尾出队元素 = " + pollLast + "，队尾出队后 deque = " + string.Join(" ", deque.toArray()));
            int pollFirst = deque.pollFirst();
            Console.WriteLine("队首出队元素 = " + pollFirst + "，队首出队后 deque = " + string.Join(" ", deque.toArray()));

            /* 获取双向队列的长度 */
            int size = deque.size();
            Console.WriteLine("双向队列长度 size = " + size);

            /* 判断双向队列是否为空 */
            bool isEmpty = deque.isEmpty();
            Console.WriteLine("双向队列是否为空 = " + isEmpty);
        }
    }
}