ABC402-D Line Crossing

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 3");
            WillReturn.Add("1 5");
            WillReturn.Add("1 8");
            WillReturn.Add("2 4");
            //2
        }
        else if (InputPattern == "Input2") {
            WillReturn.Add("5 10");
            WillReturn.Add("2 5");
            WillReturn.Add("1 5");
            WillReturn.Add("1 2");
            WillReturn.Add("2 4");
            WillReturn.Add("2 3");
            WillReturn.Add("1 3");
            WillReturn.Add("1 4");
            WillReturn.Add("3 5");
            WillReturn.Add("3 4");
            WillReturn.Add("4 5");
            //40
        }
        else {
            string wkStr;
            while ((wkStr = Console.ReadLine()) != null) WillReturn.Add(wkStr);
        }
        return WillReturn;
    }

    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 N = wkArr[0];
        long M = wkArr[1];

        var KatamukiCntDict = new Dictionary<long, long>();
        foreach (string EachStr in InputList.Skip(1)) {
            SplitAct(EachStr);
            long A = wkArr[0];
            long B = wkArr[1];
            long KatamukiID = (A + B) % N;
            if (KatamukiCntDict.ContainsKey(KatamukiID) == false) {
                KatamukiCntDict[KatamukiID] = 0;
            }
            KatamukiCntDict[KatamukiID]++;
        }

        long Answer = M * (M - 1) / 2;

        foreach (long EachCnt in KatamukiCntDict.Values) {
            if (EachCnt >= 2) {
                Answer -= EachCnt * (EachCnt - 1) / 2;
            }
        }
        Console.WriteLine(Answer);
    }
}

解説