ABC427-E Wind Cleaning

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

    static long[] GetSplitArr(string pStr)
    {
        return (pStr == "" ? new string[0] : pStr.Split(' ')).Select(pX => long.Parse(pX)).ToArray();
    }

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

    static int mTakaX;
    static int mTakaY;

    static void Main()
    {
        List<string> InputList = GetInputList();
        mBanArr = CreateBanArr(InputList.Skip(1));
        UB_X = mBanArr.GetUpperBound(0);
        UB_Y = mBanArr.GetUpperBound(1);

        for (int X = 0; X <= UB_X; X++) {
            for (int Y = 0; Y <= UB_Y; Y++) {
                if (mBanArr[X, Y] == 'T') {
                    mTakaX = X;
                    mTakaY = Y;
                }
            }
        }

        var Que = new Queue<JyoutaiDef>();
        JyoutaiDef WillEnqueue;
        WillEnqueue.Cost = 0;
        WillEnqueue.ByteArr = new byte[UB_X + 1, UB_Y + 1];
        for (int X = 0; X <= UB_X; X++) {
            for (int Y = 0; Y <= UB_Y; Y++) {
                if (mBanArr[X, Y] == '#') {
                    WillEnqueue.ByteArr[X, Y] = 1;
                }
            }
        }
        Que.Enqueue(WillEnqueue);

        var VisitedSet = new HashSet<string>();
        while (Que.Count > 0) {
            JyoutaiDef Dequeued = Que.Dequeue();
            byte[,] CurrByteArr = Dequeued.ByteArr;

            if (IsClear(CurrByteArr)) {
                Console.WriteLine(Dequeued.Cost);
                return;
            }

            Action<int, int> EnqueueAct = (pVectX, pVectY) =>
            {
                byte[,] NewByteArr = new byte[UB_X + 1, UB_Y + 1];
                for (int X = 0; X <= UB_X; X++) {
                    int TargetX = X + pVectX;
                    if (TargetX < 0 || UB_X < TargetX) continue;

                    for (int Y = 0; Y <= UB_Y; Y++) {
                        int TargetY = Y + pVectY;
                        if (TargetY < 0 || UB_Y < TargetY) continue;

                        if (CurrByteArr[X, Y] == 1) {
                            if (TargetX == mTakaX && TargetY == mTakaY) return;
                        }

                        NewByteArr[TargetX, TargetY] = CurrByteArr[X, Y];
                    }
                }

                string Hash = GetHash(NewByteArr);
                if (VisitedSet.Add(Hash)) {
                    WillEnqueue.Cost = Dequeued.Cost + 1;
                    WillEnqueue.ByteArr = NewByteArr;
                    Que.Enqueue(WillEnqueue);
                }
            };
            EnqueueAct(0, -1);
            EnqueueAct(0, +1);
            EnqueueAct(-1, 0);
            EnqueueAct(+1, 0);
        }
        Console.WriteLine(-1);
    }

    // クリア判定
    static bool IsClear(byte[,] pByteArr)
    {
        for (int X = 0; X <= UB_X; X++) {
            for (int Y = 0; Y <= UB_Y; Y++) {
                if (pByteArr[X, Y] == 1) return false;
            }
        }
        return true;
    }

    struct JyoutaiDef
    {
        internal int Cost;
        internal byte[,] ByteArr;
    }

    static string GetHash(byte[,] pByteArr)
    {
        var sb = new System.Text.StringBuilder();
        for (int X = 0; X <= UB_X; X++) {
            for (int Y = 0; Y <= UB_Y; Y++) {
                sb.Append(pByteArr[X, Y]);
            }
        }
        return sb.ToString();
    }

    ////////////////////////////////////////////////////////////////
    // IEnumerable<string>をcharの2次元配列に設定
    ////////////////////////////////////////////////////////////////
    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

盤面を状態に持って、再訪防止のBFSで解いてます。

横幅および縦幅が最大でも12マスなので
ゴミの数は最大で12*12 = 144個
それぞれのゴミの場所も 12*12=144通り

なので状態は最大でも12**4 = 20736通り
遷移で4通りしかないので
再訪防止のBFSで解けます。