ABC246-E Bishop 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("5");
            WillReturn.Add("1 3");
            WillReturn.Add("3 5");
            WillReturn.Add("....#");
            WillReturn.Add("...#.");
            WillReturn.Add(".....");
            WillReturn.Add(".#...");
            WillReturn.Add("#....");
            //3
        }
        else if (InputPattern == "Input2") {
            WillReturn.Add("4");
            WillReturn.Add("3 2");
            WillReturn.Add("4 2");
            WillReturn.Add("....");
            WillReturn.Add("....");
            WillReturn.Add("....");
            WillReturn.Add("....");
            //-1
        }
        else if (InputPattern == "Input3") {
            WillReturn.Add("18");
            WillReturn.Add("18 1");
            WillReturn.Add("1 18");
            WillReturn.Add("..................");
            WillReturn.Add(".####.............");
            WillReturn.Add(".#..#..####.......");
            WillReturn.Add(".####..#..#..####.");
            WillReturn.Add(".#..#..###...#....");
            WillReturn.Add(".#..#..#..#..#....");
            WillReturn.Add(".......####..#....");
            WillReturn.Add(".............####.");
            WillReturn.Add("..................");
            WillReturn.Add("..................");
            WillReturn.Add(".####.............");
            WillReturn.Add("....#..#..#.......");
            WillReturn.Add(".####..#..#..####.");
            WillReturn.Add(".#.....####..#....");
            WillReturn.Add(".####.....#..####.");
            WillReturn.Add("..........#..#..#.");
            WillReturn.Add(".............####.");
            WillReturn.Add("..................");
            //9
        }
        else {
            string wkStr;
            while ((wkStr = Console.ReadLine()) != null) WillReturn.Add(wkStr);
        }
        return WillReturn;
    }

    static int mStaX;
    static int mStaY;
    static int mGoalX;
    static int mGoalY;

    static char[,] mBanArr;
    static int UB_X;
    static int UB_Y;

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

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

        SplitAct(InputList[1]);
        mStaX = wkArr[1] - 1;
        mStaY = wkArr[0] - 1;

        SplitAct(InputList[2]);
        mGoalX = wkArr[1] - 1;
        mGoalY = wkArr[0] - 1;

        mBanArr = CreateBanArr(InputList.Skip(3));
        UB_X = mBanArr.GetUpperBound(0);
        UB_Y = mBanArr.GetUpperBound(1);

        ExecBFS();
    }

    struct JyoutaiDef
    {
        internal int Curr_X;
        internal int Curr_Y;
        internal int Vect_X;
        internal int Vect_Y;
        internal int Level;
    }

    static void ExecBFS()
    {
        var Que = new Queue<JyoutaiDef>();
        JyoutaiDef WillEnqueue;
        WillEnqueue.Curr_X = mStaX;
        WillEnqueue.Curr_Y = mStaY;
        WillEnqueue.Vect_X = 0;
        WillEnqueue.Vect_Y = 0;
        WillEnqueue.Level = 0;
        Que.Enqueue(WillEnqueue);

        // 最小手数[ハッシュ値]
        var MemoDict = new Dictionary<int, int>();

        while (Que.Count > 0) {
            JyoutaiDef Dequeued = Que.Dequeue();

            // クリア判定
            if (Dequeued.Curr_X == mGoalX && Dequeued.Curr_Y == mGoalY) {
                Console.WriteLine(Dequeued.Level);
                return;
            }

            Action<int, int> EnqueueAct = (pVect_X, pVect_Y) =>
            {
                // 前の移動のベクトルと、同じベクトルの場合
                if (Dequeued.Vect_X == pVect_X && Dequeued.Vect_Y == pVect_Y) {
                    return;
                }

                // 前の移動のベクトルの、逆ベクトルの場合
                if (-Dequeued.Vect_X == pVect_X && -Dequeued.Vect_Y == pVect_Y) {
                    return;
                }

                int CurrX = Dequeued.Curr_X;
                int CurrY = Dequeued.Curr_Y;
                while (true) {
                    CurrX += pVect_X;
                    CurrY += pVect_Y;
                    if (CurrX < 0 || UB_X < CurrX) return;
                    if (CurrY < 0 || UB_Y < CurrY) return;
                    if (mBanArr[CurrX, CurrY] == '#') return;

                    WillEnqueue.Curr_X = CurrX;
                    WillEnqueue.Curr_Y = CurrY;
                    WillEnqueue.Vect_X = pVect_X;
                    WillEnqueue.Vect_Y = pVect_Y;
                    WillEnqueue.Level = Dequeued.Level + 1;
                    int Hash = GetHash(WillEnqueue);
                    if (MemoDict.ContainsKey(Hash)) {
                        if (MemoDict[Hash] < WillEnqueue.Level) {
                            return;
                        }
                    }
                    MemoDict[Hash] = WillEnqueue.Level;
                    Que.Enqueue(WillEnqueue);
                }
            };

            EnqueueAct(-1, -1);
            EnqueueAct(-1, 1);
            EnqueueAct(1, -1);
            EnqueueAct(1, 1);
        }
        Console.WriteLine(-1);
    }

    static int GetHash(JyoutaiDef pJyoutai)
    {
        return pJyoutai.Curr_X * 10000 + pJyoutai.Curr_Y;
    }

    ////////////////////////////////////////////////////////////////
    // IEnumerable<string>をcharの2次元配列に設定する
    ////////////////////////////////////////////////////////////////
    static char[,] CreateBanArr(IEnumerable<string> pStrEnum)
    {
        var StrList = pStrEnum.ToList();
        if (StrList.Count == 0) {
            return new char[0, 0];
        }
        int UB_X = StrList[0].Length - 1;
        int UB_Y = StrList.Count - 1;

        char[,] WillReturn = new char[UB_X + 1, UB_Y + 1];

        for (int Y = 0; Y <= UB_Y; Y++) {
            for (int X = 0; X <= UB_X; X++) {
                WillReturn[X, Y] = StrList[Y][X];
            }
        }
        return WillReturn;
    }
}

解説

BFSで解いてますが、TLE対策で
下記の枝切りをしてます。

枝切りその1
座標ごとに移動可能な最小レベルを覚えておき
これより小さいレベルでの訪問を許可する。

枝切りその2
前回の移動のベクトルを覚えておき、
次の移動では、
同じベクトルでの移動は行わない。
逆ベクトルでの移動も行わない。