ABC153-E Crested Ibis vs Monster

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("9 3");
            WillReturn.Add("8 3");
            WillReturn.Add("4 2");
            WillReturn.Add("2 1");
            //4
        }
        else if (InputPattern == "Input2") {
            WillReturn.Add("100 6");
            WillReturn.Add("1 1");
            WillReturn.Add("2 3");
            WillReturn.Add("3 9");
            WillReturn.Add("4 27");
            WillReturn.Add("5 81");
            WillReturn.Add("6 243");
            //100
        }
        else if (InputPattern == "Input3") {
            WillReturn.Add("9999 10");
            WillReturn.Add("540 7550");
            WillReturn.Add("691 9680");
            WillReturn.Add("700 9790");
            WillReturn.Add("510 7150");
            WillReturn.Add("415 5818");
            WillReturn.Add("551 7712");
            WillReturn.Add("587 8227");
            WillReturn.Add("619 8671");
            WillReturn.Add("588 8228");
            WillReturn.Add("176 2461");
            //139815
        }
        else {
            string wkStr;
            while ((wkStr = Console.ReadLine()) != null) WillReturn.Add(wkStr);
        }
        return WillReturn;
    }

    struct ABInfoDef
    {
        internal long A;
        internal long B;
    }

    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]);
        long H = wkArr[0];
        long UB = H;

        var ABInfoList = new List<ABInfoDef>();
        foreach (string EachStr in InputList.Skip(1)) {
            SplitAct(EachStr);
            ABInfoDef WillAdd;
            WillAdd.A = wkArr[0];
            WillAdd.B = wkArr[1];
            ABInfoList.Add(WillAdd);
        }

        // 最小の消費魔力[モンスターのHP]なDP表
        long?[] DPArr = new long?[UB + 1];
        DPArr[UB] = 0;

        foreach (ABInfoDef EachABInfo in ABInfoList) {
            for (long I = UB; 1 <= I; I--) {
                if (DPArr[I].HasValue == false) continue;

                long NewInd = I - EachABInfo.A;
                NewInd = Math.Max(0, NewInd);

                long NewVal = DPArr[I].Value + EachABInfo.B;

                if (DPArr[NewInd].HasValue) {
                    if (DPArr[NewInd].Value <= NewVal) {
                        continue;
                    }
                }
                DPArr[NewInd] = NewVal;
            }
        }
        Console.WriteLine(DPArr[0]);
    }
}

解説

DPで解いてます。