ABC154-E Almost Everywhere Zero

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("100");
            WillReturn.Add("1");
            //19
        }
        else if (InputPattern == "Input2") {
            WillReturn.Add("25");
            WillReturn.Add("2");
            //14
        }
        else if (InputPattern == "Input3") {
            WillReturn.Add("314159");
            WillReturn.Add("2");
            //937
        }
        else if (InputPattern == "Input4") {
            WillReturn.Add("9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999");
            WillReturn.Add("3");
            //117879300
        }
        else {
            string wkStr;
            while ((wkStr = Console.ReadLine()) != null) WillReturn.Add(wkStr);
        }
        return WillReturn;
    }

    struct JyoutaiDef
    {
        internal bool FreeNum; // 数字自由フラグ
        internal long NonZeroCnt; // ゼロ以外数字の数
    }

    static void Main()
    {
        List<string> InputList = GetInputList();
        string StrN = InputList[0];
        long K = long.Parse(InputList[1]);

        // 場合の数[状態定義]なDP表
        var PrevDP = new Dictionary<JyoutaiDef, long>();
        JyoutaiDef FirstJyoutai;
        FirstJyoutai.NonZeroCnt = 0;
        FirstJyoutai.FreeNum = false;
        PrevDP[FirstJyoutai] = 1;

        for (int I = 0; I <= StrN.Length - 1; I++) {
            var CurrDP = new Dictionary<JyoutaiDef, long>();
            foreach (var EachPair in PrevDP) {
                for (char NewChar = '0'; NewChar <= '9'; NewChar++) {
                    if (EachPair.Key.FreeNum == false && StrN[I] < NewChar) break;

                    bool NewFreeNum = EachPair.Key.FreeNum;
                    if (StrN[I] > NewChar) NewFreeNum = true;

                    long NewNonZeroCnt = EachPair.Key.NonZeroCnt;
                    if (NewChar != '0') {
                        NewNonZeroCnt++;
                    }

                    // 枝切り
                    if (NewNonZeroCnt > K) continue;

                    JyoutaiDef NewJyoutai;
                    NewJyoutai.NonZeroCnt = NewNonZeroCnt;
                    NewJyoutai.FreeNum = NewFreeNum;
                    if (CurrDP.ContainsKey(NewJyoutai) == false) {
                        CurrDP[NewJyoutai] = 0;
                    }
                    CurrDP[NewJyoutai] += EachPair.Value;
                }
            }
            PrevDP = CurrDP;
        }
        long Answer = 0;
        foreach (var EachPair in PrevDP) {
            if (EachPair.Key.NonZeroCnt == K) {
                Answer += EachPair.Value;
            }
        }
        Console.WriteLine(Answer);
    }
}

解説

桁DPで解いてます。