ABC240-E Ranges on Tree

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("2 1");
            WillReturn.Add("3 1");
            //1 2
            //2 2
            //1 1
        }
        else if (InputPattern == "Input2") {
            WillReturn.Add("5");
            WillReturn.Add("3 4");
            WillReturn.Add("5 4");
            WillReturn.Add("1 2");
            WillReturn.Add("1 4");
            //1 3
            //3 3
            //2 2
            //1 2
            //1 1
        }
        else if (InputPattern == "Input3") {
            WillReturn.Add("5");
            WillReturn.Add("4 5");
            WillReturn.Add("3 2");
            WillReturn.Add("5 2");
            WillReturn.Add("3 1");
            //1 1
            //1 1
            //1 1
            //1 1
            //1 1
        }
        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();
    }

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

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

        long NodeCnt = long.Parse(InputList[0]);

        long[] wkArr = { };
        Action<string> SplitAct = (pStr) => wkArr = GetSplitArr(pStr);

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

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

        List<JyoutaiDef> DFSResult = ExecDFS(1);
        DFSResult.Reverse();

        // 葉ノード以外のノードのset
        var NonLeafNodeSet = new HashSet<long>();

        // リーフ番号の最小値[ノード]
        var MinLeafDict = new Dictionary<long, long>();

        // リーフ番号の最大値[ノード]
        var MaxLeafDict = new Dictionary<long, long>();

        for (long I = 1; I <= NodeCnt; I++) {
            MinLeafDict[I] = long.MaxValue;
        }
        for (long I = 1; I <= NodeCnt; I++) {
            MaxLeafDict[I] = long.MinValue;
        }

        long CurrLeafNo = 1;
        foreach (JyoutaiDef EachJyoutai in DFSResult) {
            long ParentNode = EachJyoutai.ParentNode;
            long CurrNode = EachJyoutai.Node;
            NonLeafNodeSet.Add(EachJyoutai.ParentNode);

            if (NonLeafNodeSet.Contains(CurrNode) == false) {
                MinLeafDict[CurrNode] = CurrLeafNo;
                MaxLeafDict[CurrNode] = CurrLeafNo;
                CurrLeafNo++;
            }

            if (ParentNode != -1) {
                MinLeafDict[ParentNode] = Math.Min(MinLeafDict[ParentNode], MinLeafDict[CurrNode]);
                MaxLeafDict[ParentNode] = Math.Max(MaxLeafDict[ParentNode], MaxLeafDict[CurrNode]);
            }
        }

        for (long I = 1; I <= NodeCnt; I++) {
            long MinLeaf = MinLeafDict[I];
            long MaxLeaf = MaxLeafDict[I];
            Console.WriteLine("{0} {1}", MinLeaf, MaxLeaf);
        }
    }

    struct JyoutaiDef
    {
        internal int Node;
        internal int ParentNode;
    }

    static List<JyoutaiDef> ExecDFS(int pRootNode)
    {
        var WillReturn = new List<JyoutaiDef>();

        var Stk = new Stack<JyoutaiDef>();
        JyoutaiDef WillPush;
        WillPush.Node = pRootNode;
        WillPush.ParentNode = -1;
        Stk.Push(WillPush);

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

        while (Stk.Count > 0) {
            JyoutaiDef Popped = Stk.Pop();
            WillReturn.Add(Popped);
            if (mToNodeListDict.ContainsKey(Popped.Node)) {
                foreach (int EachToNode in mToNodeListDict[Popped.Node]) {
                    if (VisitedSet.Add(EachToNode)) {
                        WillPush.Node = EachToNode;
                        WillPush.ParentNode = Popped.Node;
                        Stk.Push(WillPush);
                    }
                }
            }
        }
        return WillReturn;
    }
}

解説

問題を読解すると、
木の葉ノードに連番を振る。
木の葉から根に向かって木DPを行い、
葉ノードの最小と最大を更新すれば良いと分かります。