B62 Print a Path

問題へのリンク

C#のソース(オイラーツアーを使う方法)

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 4");
            WillReturn.Add("1 2");
            WillReturn.Add("2 3");
            WillReturn.Add("3 4");
            WillReturn.Add("3 5");
            //1 2 3 5 
        }
        else if (InputPattern == "Input2") {
            WillReturn.Add("15 30");
            WillReturn.Add("6 9");
            WillReturn.Add("9 10");
            WillReturn.Add("2 9");
            WillReturn.Add("9 12");
            WillReturn.Add("2 14");
            WillReturn.Add("1 4");
            WillReturn.Add("4 6");
            WillReturn.Add("1 3");
            WillReturn.Add("4 14");
            WillReturn.Add("1 6");
            WillReturn.Add("9 11");
            WillReturn.Add("2 6");
            WillReturn.Add("3 9");
            WillReturn.Add("5 9");
            WillReturn.Add("4 9");
            WillReturn.Add("11 15");
            WillReturn.Add("1 13");
            WillReturn.Add("4 13");
            WillReturn.Add("8 9");
            WillReturn.Add("9 13");
            WillReturn.Add("5 15");
            WillReturn.Add("3 5");
            WillReturn.Add("8 10");
            WillReturn.Add("2 4");
            WillReturn.Add("9 14");
            WillReturn.Add("1 9");
            WillReturn.Add("2 8");
            WillReturn.Add("6 13");
            WillReturn.Add("7 9");
            WillReturn.Add("9 15");
            //1 4 6 9 11 15 
        }
        else {
            string wkStr;
            while ((wkStr = Console.ReadLine()) != null) WillReturn.Add(wkStr);
        }
        return WillReturn;
    }

    static int mN;

    // 隣接リスト
    static Dictionary<int, List<int>> mToNodeListDict = new Dictionary<int, List<int>>();

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

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

        SplitAct(InputList[0]);
        mN = wkArr[0];

        foreach (string EachStr in InputList.Skip(1)) {
            SplitAct(EachStr);
            int FromNode = wkArr[0];
            int ToNode = wkArr[1];

            if (mToNodeListDict.ContainsKey(FromNode) == false) {
                mToNodeListDict[FromNode] = new List<int>();
            }
            if (mToNodeListDict.ContainsKey(ToNode) == false) {
                mToNodeListDict[ToNode] = new List<int>();
            }
            mToNodeListDict[FromNode].Add(ToNode);
            mToNodeListDict[ToNode].Add(FromNode);
        }
        ExecEulerTour();

        var AnswerList = new List<int>();
        foreach (JyoutaiDef EachJyoutai in mEulerTourJyoutaiList) {
            if (EachJyoutai.IsStart) {
                AnswerList.Add(EachJyoutai.Node);
                if (EachJyoutai.Node == mN) {
                    break;
                }
            }
            if (EachJyoutai.IsEnd) {
                AnswerList.RemoveAt(AnswerList.Count - 1);
            }
        }

        Console.WriteLine(IntEnumJoin(" ", AnswerList));
    }

    struct JyoutaiDef
    {
        internal int Node;
        internal int Level;
        internal bool IsStart;
        internal bool IsEnd;
    }

    // オイラーツアーを行い、下記の2通りのタイミングでノードをAddする
    // 1 最初の訪問時
    // 2 子の部分木を訪問完了時
    static List<JyoutaiDef> mEulerTourJyoutaiList = new List<JyoutaiDef>();
    static void ExecEulerTour()
    {
        var Stk = new Stack<JyoutaiDef>();
        JyoutaiDef WillPush;
        WillPush.Node = 1;
        WillPush.Level = 0;

        WillPush.IsStart = false; WillPush.IsEnd = true;
        Stk.Push(WillPush);
        WillPush.IsStart = true; WillPush.IsEnd = false;
        Stk.Push(WillPush);

        var VisitedSet = new HashSet<int>();
        VisitedSet.Add(1);

        while (Stk.Count > 0) {
            JyoutaiDef Popped = Stk.Pop();
            mEulerTourJyoutaiList.Add(Popped);
            if (Popped.IsEnd) {
                continue;
            }
            if (mToNodeListDict.ContainsKey(Popped.Node)) {
                foreach (int EachToNode in mToNodeListDict[Popped.Node]) {
                    if (VisitedSet.Add(EachToNode)) {
                        WillPush.Node = EachToNode;
                        WillPush.Level = Popped.Level + 1;

                        WillPush.IsStart = false; WillPush.IsEnd = true;
                        Stk.Push(WillPush);
                        WillPush.IsStart = true; WillPush.IsEnd = false;
                        Stk.Push(WillPush);
                    }
                }
            }
        }
    }

    // セパレータとInt型の列挙を引数として、結合したstringを返す
    static string IntEnumJoin(string pSeparater, IEnumerable<int> pEnum)
    {
        string[] StrArr = Array.ConvertAll(pEnum.ToArray(), pX => pX.ToString());
        return string.Join(pSeparater, StrArr);
    }
}

C#のソース(再帰を使う方法)

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

class Program
{
    static string InputPattern = "InputX";

    static List<string> GetInputList()
    {
        var WillReturn = new List<string>();
        string wkStr;
        while ((wkStr = Console.ReadLine()) != null) WillReturn.Add(wkStr);
        return WillReturn;
    }

    static int mN;

    // 隣接リスト
    static Dictionary<int, List<int>> mToNodeListDict = new Dictionary<int, List<int>>();

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

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

        SplitAct(InputList[0]);
        mN = wkArr[0];

        foreach (string EachStr in InputList.Skip(1)) {
            SplitAct(EachStr);
            int FromNode = wkArr[0];
            int ToNode = wkArr[1];

            if (mToNodeListDict.ContainsKey(FromNode) == false) {
                mToNodeListDict[FromNode] = new List<int>();
            }
            if (mToNodeListDict.ContainsKey(ToNode) == false) {
                mToNodeListDict[ToNode] = new List<int>();
            }
            mToNodeListDict[FromNode].Add(ToNode);
            mToNodeListDict[ToNode].Add(FromNode);
        }
        dfs(1);
    }

    static List<int> mPathList = new List<int>();
    static HashSet<int> mVisitedSet = new HashSet<int>();
    static bool mFoundAnswer = false;

    static void dfs(int pCurrNode)
    {
        if (mFoundAnswer) return;

        mPathList.Add(pCurrNode);
        mVisitedSet.Add(pCurrNode);
        if (mVisitedSet.Contains(mN)) {
            mFoundAnswer = true;
            Console.WriteLine(IntEnumJoin(" ", mPathList));
            return;
        }

        if (mToNodeListDict.ContainsKey(pCurrNode)) {
            foreach (int EachToNode in mToNodeListDict[pCurrNode]) {
                if (mVisitedSet.Add(EachToNode)) {
                    dfs(EachToNode);
                }
            }
        }
        mPathList.RemoveAt(mPathList.Count - 1);
    }

    // セパレータとInt型の列挙を引数として、結合したstringを返す
    static string IntEnumJoin(string pSeparater, IEnumerable<int> pEnum)
    {
        string[] StrArr = Array.ConvertAll(pEnum.ToArray(), pX => pX.ToString());
        return string.Join(pSeparater, StrArr);
    }
}

解説

オイラツアーや
再帰によるdfsで、解けます。