ABC155-E Payment

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("36");
            //8
        }
        else if (InputPattern == "Input2") {
            WillReturn.Add("91");
            //3
        }
        else if (InputPattern == "Input3") {
            WillReturn.Add("314159265358979323846264338327950288419716939937551058209749445923078164062862089986280348253421170");
            //243
        }
        else {
            string wkStr;
            while ((wkStr = Console.ReadLine()) != null) WillReturn.Add(wkStr);
        }
        return WillReturn;
    }

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

        // 最小コスト[繰り上がり有無] なDP表
        var PrevDP = new Dictionary<bool, long>();
        PrevDP[false] = 0;

        foreach (char EachChar in StrN.ToCharArray().Reverse()) {
            var CurrDP = new Dictionary<bool, long>();

            foreach (var EachPair in PrevDP) {
                int CurrNum = EachChar - '0';
                if (EachPair.Key) {
                    CurrNum++;
                }

                Action<bool, long> UpdateAct = (pNewKey, pNewVal) =>
                {
                    if (CurrDP.ContainsKey(pNewKey)) {
                        if (CurrDP[pNewKey] <= pNewVal) {
                            return;
                        }
                    }
                    CurrDP[pNewKey] = pNewVal;
                };

                // 今の桁で払う場合
                UpdateAct(false, EachPair.Value + CurrNum);

                // 次の桁で支払い、今の桁でおつりを貰う場合
                UpdateAct(true, EachPair.Value + 10 - CurrNum);
            }
            PrevDP = CurrDP;
        }

        long Answer = long.MaxValue;
        foreach (var EachPair in PrevDP) {
            if (EachPair.Key) {
                Answer = Math.Min(Answer, EachPair.Value + 1);
            }
            else {
                Answer = Math.Min(Answer, EachPair.Value);
            }
        }
        Console.WriteLine(Answer);
    }
}

解説

下位桁から、
最小コスト[繰り上がり有無]でDPしてます。