B56 Palindrome Queries

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("11 3");
            WillReturn.Add("mississippi");
            WillReturn.Add("5 8");
            WillReturn.Add("6 10");
            WillReturn.Add("2 8");
            //Yes
            //No
            //Yes
        }
        else {
            string wkStr;
            while ((wkStr = Console.ReadLine()) != null) WillReturn.Add(wkStr);
        }
        return WillReturn;
    }

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

        string SeiS = InputList[1];
        string RevS = new string(SeiS.ToCharArray().Reverse().ToArray());

        int UB = SeiS.Length - 1;

        var InsRollingHashSei = new RollingHash(SeiS);
        var InsRollingHashRev = new RollingHash(RevS);

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

        foreach (string EachStr in InputList.Skip(2)) {
            SplitAct(EachStr);
            int L = wkArr[0] - 1;
            int R = wkArr[1] - 1;

            int RevL = UB - L;
            int RevR = UB - R;

            decimal Hash1 = InsRollingHashSei.GetRangeHash(L, R);
            decimal Hash2 = InsRollingHashRev.GetRangeHash(RevR, RevL);

            if (Hash1 == Hash2) {
                Console.WriteLine("Yes");
            }
            else {
                Console.WriteLine("No");
            }
        }
    }
}

#region RollingHash
// ローリングハッシュ
internal class RollingHash
{
    const decimal Base = 100M;
    const decimal Hou = 67280421310721M;

    // ハッシュ値[終了Ind]で、[0,終了Ind]のハッシュ値を保持
    internal decimal[] mHashArr;

    // 桁の重みの配列
    decimal[] mOmomiArr;

    // コンストラクタ
    internal RollingHash(string pTargetStr)
    {
        decimal Omomi = 1;
        long UB = pTargetStr.Length - 1;

        mHashArr = new decimal[UB + 1];
        mOmomiArr = new decimal[UB + 1];
        for (int I = 0; I <= UB; I++) {
            mOmomiArr[I] = Omomi;
            if (I > 0) {
                mHashArr[I] += mHashArr[I - 1] * Base;
                mHashArr[I] %= Hou;
            }
            mHashArr[I] += pTargetStr[I];
            mHashArr[I] %= Hou;
            Omomi *= Base;
            Omomi %= Hou;
        }
    }

    // [Sta,End]のハッシュ値を返す
    internal decimal GetRangeHash(long pSta, long pEnd)
    {
        decimal WillReturn = mHashArr[pEnd];
        if (pSta > 0) {
            long Range = pEnd - pSta + 1;
            decimal PrevVal = mHashArr[pSta - 1];
            decimal MinusVal = PrevVal * mOmomiArr[Range];
            MinusVal %= Hou;
            WillReturn -= MinusVal;
            if (WillReturn < 0) {
                WillReturn += Hou;
            }
        }
        return WillReturn;
    }
}
#endregion

解説

前処理で、文字列の正順と逆順でのハッシュ値を用意してます。