ABC258-D Trophy

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 4");
            WillReturn.Add("3 4");
            WillReturn.Add("2 3");
            WillReturn.Add("4 2");
            //18
        }
        else if (InputPattern == "Input2") {
            WillReturn.Add("10 1000000000");
            WillReturn.Add("3 3");
            WillReturn.Add("1 6");
            WillReturn.Add("4 7");
            WillReturn.Add("1 8");
            WillReturn.Add("5 7");
            WillReturn.Add("9 9");
            WillReturn.Add("2 4");
            WillReturn.Add("6 4");
            WillReturn.Add("5 1");
            WillReturn.Add("3 1");
            //1000000076
        }
        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();

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

        SplitAct(InputList[0]);
        long X = wkArr[1];

        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);
        }

        var AnswerKouho = new List<long>();

        long ABRunSum = 0;
        long RunMinB = ABInfoList[0].B;
        long StageCnt = 0;

        foreach (ABInfoDef EachABInfo in ABInfoList) {
            ABRunSum += EachABInfo.A + EachABInfo.B;
            RunMinB = Math.Min(RunMinB, EachABInfo.B);
            StageCnt++;

            long RestStage = X - StageCnt;
            if (RestStage < 0) break;
            long Kouho = ABRunSum + RestStage * RunMinB;
            AnswerKouho.Add(Kouho);
        }
        Console.WriteLine(AnswerKouho.Min());
    }
}

解説

どのステージまでクリアするかを全探索してます。