第2回PAST J 文字列解析

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("(ab)c");
            //abbac
        }
        else if (InputPattern == "Input2") {
            WillReturn.Add("past");
            //past
        }
        else if (InputPattern == "Input3") {
            WillReturn.Add("(d(abc)e)()");
            //dabccbaeeabccbad
        }
        else {
            string wkStr;
            while ((wkStr = Console.ReadLine()) != null) WillReturn.Add(wkStr);
        }
        return WillReturn;
    }

    static void Main()
    {
        List<string> InputList = GetInputList();
        string S = InputList[0];

        while (S.Contains('(')) {
            int Sta, End;
            DeriveStaEndPair(S, out Sta, out End);

            string InStr = S.Substring(Sta, End - Sta + 1);

            InStr = InStr.Replace("(", "").Replace(")", "");
            InStr = InStr + new string(InStr.ToCharArray().Reverse().ToArray());

            S = S.Remove(Sta, End - Sta + 1);
            S = S.Insert(Sta, InStr);
        }
        Console.WriteLine(S);
    }

    // ネストしてない括弧のStaとEndを返す
    static void DeriveStaEndPair(string pS, out int pSta, out int pEnd)
    {
        pSta = pEnd = -1;

        var StaList = new List<int>();
        var EndList = new List<int>();

        for (int I = 0; I <= pS.Length - 1; I++) {
            if (pS[I] == '(') StaList.Add(I);
            if (pS[I] == ')') EndList.Add(I);
        }

        foreach (int EachInt in StaList) {
            int Upper1 = ExecNibunhou_UpperBound(EachInt, StaList);
            int Upper2 = ExecNibunhou_UpperBound(EachInt, EndList);
            if (Upper1 > -1 && StaList[Upper1] < EndList[Upper2]) {
                continue;
            }

            pSta = EachInt;
            pEnd = EndList[Upper2];
            return;
        }
    }

    // 二分法で、Val超えで最小の値を持つ、添字を返す
    static int ExecNibunhou_UpperBound(int pVal, List<int> pList)
    {
        // 最後の要素がVal以下の特殊ケース
        if (pVal >= pList.Last()) {
            return -1;
        }
        // 最初の要素がVal超えの特殊ケース
        if (pVal < pList[0]) {
            return 0;
        }

        int L = 0;
        int R = pList.Count - 1;

        while (L + 1 < R) {
            int Mid = (L + R) / 2;

            if (pList[Mid] > pVal) {
                R = Mid;
            }
            else {
                L = Mid;
            }
        }
        return R;
    }
}

解説

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