ABC193-C Unexpressed

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("8");
            //6
        }
        else if (InputPattern == "Input2") {
            WillReturn.Add("100000");
            //99634
        }
        else {
            string wkStr;
            while ((wkStr = Console.ReadLine()) != null) WillReturn.Add(wkStr);
        }
        return WillReturn;
    }

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

        long N = long.Parse(InputList[0]);

        var ProdSet = new HashSet<long>();
        for (long A = 2; A * A <= N; A++) {
            long ProdVal = A;
            for (long B = 2; B < long.MaxValue; B++) {
                ProdVal *= A;

                if (ProdVal <= N) {
                    ProdSet.Add(ProdVal);
                }
                if (ProdVal > N) break;
            }
        }
        Console.WriteLine(N - ProdSet.Count);
    }
}

解説

2以上のAとBを全探索してます。