ABC268-D Unique Username

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("1 1");
            WillReturn.Add("chokudai");
            WillReturn.Add("chokudai");
            //-1
        }
        else if (InputPattern == "Input2") {
            WillReturn.Add("2 2");
            WillReturn.Add("choku");
            WillReturn.Add("dai");
            WillReturn.Add("chokudai");
            WillReturn.Add("choku_dai");
            //dai_choku
        }
        else if (InputPattern == "Input3") {
            WillReturn.Add("2 2");
            WillReturn.Add("chokudai");
            WillReturn.Add("atcoder");
            WillReturn.Add("chokudai_atcoder");
            WillReturn.Add("atcoder_chokudai");
            //-1
        }
        else if (InputPattern == "Input4") {
            WillReturn.Add("4 4");
            WillReturn.Add("ab");
            WillReturn.Add("cd");
            WillReturn.Add("ef");
            WillReturn.Add("gh");
            WillReturn.Add("hoge");
            WillReturn.Add("fuga");
            WillReturn.Add("____");
            WillReturn.Add("_ab_cd_ef_gh_");
            //ab__ef___cd_gh
        }
        else {
            string wkStr;
            while ((wkStr = Console.ReadLine()) != null) WillReturn.Add(wkStr);
        }
        return WillReturn;
    }

    static void Main()
    {
        List<string> InputList = GetInputList();
        int[] wkArr = InputList[0].Split(' ').Select(pX => int.Parse(pX)).ToArray();
        int N = wkArr[0];
        int M = wkArr[1];

        var SList = new List<string>();
        foreach (string EachStr in InputList.Skip(1).Take(N)) {
            SList.Add(EachStr);
        }

        // 可能な_の最大数
        var SpaceList = new List<string>();
        int SpaceLimit = 16 - SList.Sum(pX => pX.Length);
        if (SList.Count >= 3) {
            SpaceLimit -= SList.Count - 2;
        }

        for (int I = 1; I <= SpaceLimit; I++) {
            SpaceList.Add(new string('_', I));
        }

        var TSet = new HashSet<string>();
        foreach (string EachStr in InputList.Skip(1 + N)) {
            TSet.Add(EachStr);
        }

        var Stk = new Stack<JyoutaiDef>();
        JyoutaiDef WillPush;
        WillPush.SelectedIndList = new List<int>();
        WillPush.CurrStr = "";
        Stk.Push(WillPush);

        while (Stk.Count > 0) {
            JyoutaiDef Popped = Stk.Pop();

            if (Popped.CurrStr.Length > 16) continue;
            if (Popped.SelectedIndList.Count == SList.Count) {
                if (Popped.CurrStr.Length >= 3) {
                    if (TSet.Contains(Popped.CurrStr) == false) {
                        Console.WriteLine(Popped.CurrStr);
                        return;
                    }
                }
                continue;
            }

            for (int I = 0; I <= SList.Count - 1; I++) {
                if (Popped.SelectedIndList.Contains(I)) continue;
                WillPush.SelectedIndList = new List<int>(Popped.SelectedIndList);
                WillPush.SelectedIndList.Add(I);

                if (WillPush.SelectedIndList.Count == 1) {
                    WillPush.CurrStr = SList[I];
                    Stk.Push(WillPush);
                }
                else {
                    foreach (string EachSpace in SpaceList) {
                        WillPush.CurrStr = Popped.CurrStr + EachSpace + SList[I];
                        int RestLen = 16 - WillPush.CurrStr.Length;
                        int NeedLen = 0;
                        for (int J = 0; J <= SList.Count - 1; J++) {
                            if (WillPush.SelectedIndList.Contains(J)) continue;
                            NeedLen += SList[J].Length;
                            NeedLen++; // 文字列の間の分
                        }
                        NeedLen--; // 文字列の間を余計に計上してるので、1引く

                        // 枝切り
                        if (NeedLen > RestLen) break;

                        Stk.Push(WillPush);
                    }
                }
            }
        }
        Console.WriteLine(-1);
    }
}

struct JyoutaiDef
{
    internal List<int> SelectedIndList;
    internal string CurrStr;
}

解説

DFSで解候補を列挙してます。