AOJ 0535 薄氷渡り

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");
            WillReturn.Add("3");
            WillReturn.Add("1 1 0");
            WillReturn.Add("1 0 1");
            WillReturn.Add("1 1 0");
            WillReturn.Add("5");
            WillReturn.Add("3");
            WillReturn.Add("1 1 1 0 1");
            WillReturn.Add("1 1 0 0 0");
            WillReturn.Add("1 0 0 0 1");
            WillReturn.Add("0");
            WillReturn.Add("0");
            //5
            //5
        }
        else {
            string wkStr;
            while ((wkStr = Console.ReadLine()) != null) WillReturn.Add(wkStr);
        }
        return WillReturn;
    }

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

        int CurrInd = 0;
        while (true) {
            int Width = int.Parse(InputList[CurrInd]);
            int Height = int.Parse(InputList[CurrInd + 1]);
            if (Width == 0 && Height == 0) break;
            mBanArr = CreateBanArr(InputList.Skip(CurrInd + 2).Take(Height));
            Solve();

            CurrInd += 2 + Height;
        }
    }

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

    static HashSet<int> mCntSet = new HashSet<int>();
    static HashSet<int> mVisitedSet = new HashSet<int>();

    static void Solve()
    {
        UB_X = mBanArr.GetUpperBound(0);
        UB_Y = mBanArr.GetUpperBound(1);

        mCntSet.Clear();
        mVisitedSet.Clear();

        for (int X = 0; X <= UB_X; X++) {
            for (int Y = 0; Y <= UB_Y; Y++) {
                DFS(X, Y);
            }
        }
        Console.WriteLine(mCntSet.Max());
    }

    static void DFS(int pCurrX, int pCurrY)
    {
        if (pCurrX < 0 || UB_X < pCurrX) return;
        if (pCurrY < 0 || UB_Y < pCurrY) return;
        if (mBanArr[pCurrX, pCurrY] == 0) return;

        int CurrHash = GetHash(pCurrX, pCurrY);
        if (mVisitedSet.Add(CurrHash) == false) {
            return;
        }
        mCntSet.Add(mVisitedSet.Count);

        DFS(pCurrX, pCurrY - 1);
        DFS(pCurrX, pCurrY + 1);
        DFS(pCurrX - 1, pCurrY);
        DFS(pCurrX + 1, pCurrY);

        mVisitedSet.Remove(CurrHash);
    }

    // 座標のハッシュ値を返す
    static int GetHash(int pX, int pY)
    {
        return pX * 100 + pY;
    }

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

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

        SplitAct(StrList[0]);

        int UB_X = IntArr.GetUpperBound(0);
        int UB_Y = StrList.Count - 1;

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

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

解説

状態に訪問した座標のHashSetを持つ必要があるので、
DFS木をイメージしつつ、
Stackではなく、再帰で深さ優先探索してます。