典型90問 061 Deck（★2）

問題へのリンク

C#のソース

using System;
using System.Collections.Generic;
using System.Linq;

class Program
{
    static string InputPattern = "InputX";

    static List<string> GetInputList()
    {
        var WillReturn = new List<string>();

        if (InputPattern == "Input1") {
            WillReturn.Add("6");
            WillReturn.Add("1 2");
            WillReturn.Add("1 1");
            WillReturn.Add("2 3");
            WillReturn.Add("3 1");
            WillReturn.Add("3 2");
            WillReturn.Add("3 3");
            //1
            //2
            //3
        }
        else if (InputPattern == "Input2") {
            WillReturn.Add("6");
            WillReturn.Add("2 1");
            WillReturn.Add("3 1");
            WillReturn.Add("2 2");
            WillReturn.Add("3 1");
            WillReturn.Add("2 3");
            WillReturn.Add("3 1");
            //1
            //1
            //1
        }
        else if (InputPattern == "Input3") {
            WillReturn.Add("6");
            WillReturn.Add("1 1000000000");
            WillReturn.Add("2 200000000");
            WillReturn.Add("1 30000000");
            WillReturn.Add("2 4000000");
            WillReturn.Add("1 500000");
            WillReturn.Add("3 3");
            //1000000000
        }
        else {
            string wkStr;
            while ((wkStr = Console.ReadLine()) != null) WillReturn.Add(wkStr);
        }
        return WillReturn;
    }

    static void Main()
    {
        List<string> InputList = GetInputList();

        int[] wkArr = { };
        Action<string> SplitAct = pStr =>
            wkArr = pStr.Split(' ').Select(pX => int.Parse(pX)).ToArray();

        var InsDeque = new Deque<int>();

        foreach (string EachStr in InputList.Skip(1)) {
            SplitAct(EachStr);

            int T = wkArr[0];
            int X = wkArr[1];

            if (T == 1) {
                InsDeque.PushFront(X);
            }
            if (T == 2) {
                InsDeque.PushBack(X);
            }
            if (T == 3) {
                Console.WriteLine(InsDeque[X - 1]);
            }
        }
    }
}

#region Deque
internal class Deque<T>
{
    T[] buf;
    int offset, count, capacity;

    internal int Count { get { return count; } }

    internal Deque(int cap) { buf = new T[capacity = cap]; }

    internal Deque() { buf = new T[capacity = 16]; }

    internal T this[int index]
    {
        get { return buf[GetIndex(index)]; }
        set { buf[GetIndex(index)] = value; }
    }

    private int GetIndex(int index)
    {
        if (index >= capacity)
            throw new IndexOutOfRangeException("out of range");
        int ret = index + offset;
        if (ret >= capacity)
            ret -= capacity;
        return ret;
    }

    internal void PushFront(T item)
    {
        if (count == capacity) Extend();
        if (--offset < 0) offset += buf.Length;
        buf[offset] = item;
        count++;
    }

    internal T PopFront()
    {
        if (count == 0)
            throw new InvalidOperationException("collection is empty");
        count--;
        T ret = buf[offset++];
        if (offset >= capacity) offset -= capacity;
        return ret;
    }

    internal void PushBack(T item)
    {
        if (count == capacity) Extend();
        int id = count + offset;
        count++;
        if (id >= capacity) id -= capacity;
        buf[id] = item;
    }

    internal T PopBack()
    {
        if (count == 0)
            throw new InvalidOperationException("collection is empty");
        return buf[GetIndex(--count)];
    }

    internal void Insert(int index, T item)
    {
        if (index > count) throw new IndexOutOfRangeException();
        this.PushFront(item);
        for (int i = 0; i < index; i++)
            this[i] = this[i + 1];
        this[index] = item;
    }

    internal T RemoveAt(int index)
    {
        if (index < 0 || index >= count) throw new IndexOutOfRangeException();
        T ret = this[index];
        for (int i = index; i > 0; i--)
            this[i] = this[i - 1];
        this.PopFront();
        return ret;
    }

    private void Extend()
    {
        T[] newBuffer = new T[capacity << 1];
        if (offset > capacity - count) {
            int len = buf.Length - offset;
            Array.Copy(buf, offset, newBuffer, 0, len);
            Array.Copy(buf, 0, newBuffer, len, count - len);
        }
        else Array.Copy(buf, offset, newBuffer, 0, count);
        buf = newBuffer;
        offset = 0;
        capacity <<= 1;
    }

    internal T[] Items//デバッグ時に中身を調べるためのプロパティ
    {
        get
        {
            T[] a = new T[count];
            for (int i = 0; i < count; i++)
                a[i] = this[i];
            return a;
        }
    }
}
#endregion

解説

C$のLinkedListはインデクサが使えないので
Dequeクラスを使ってます。