CodeQUEEN 2026 決勝 D ぶどうの教室

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");
            //3
            //1 1 1 2
            //1 3 2 2
            //3 1 2 1
        }
        else if (InputPattern == "Input2") {
            WillReturn.Add("2");
            //1
            //1 2 2 1
        }
        else if (InputPattern == "Input3") {
            WillReturn.Add("4");
            //5
            //1 1 1 2
            //2 2 2 1
            //3 1 4 1
            //1 4 1 3
            //3 2 2 3
        }
        else {
            string wkStr;
            while ((wkStr = Console.ReadLine()) != null) WillReturn.Add(wkStr);
        }
        return WillReturn;
    }

    static long[] GetSplitArr(string pStr)
    {
        return (pStr == "" ? new string[0] : pStr.Split(' ')).Select(pX => long.Parse(pX)).ToArray();
    }

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

        // 房の有無[X,Y]な2次元配列
        bool[,] BoolArr = new bool[N + 1 + 1, N + 1 + 1];
        long RetuCnt = N;
        for (long LoopY = 1; LoopY <= N; LoopY++) {
            for (long LoopX = 1; LoopX <= RetuCnt; LoopX++) {
                BoolArr[LoopX, LoopY] = true;
            }
            RetuCnt--;
        }

        var Answerist = new List<string>();
        for (long LoopY = 1; LoopY <= N; LoopY++) {
            for (long LoopX = 1; LoopX <= N; LoopX++) {
                if (BoolArr[LoopX, LoopY] && BoolArr[LoopX + 1, LoopY]) {
                    BoolArr[LoopX, LoopY] = false;
                    BoolArr[LoopX + 1, LoopY] = false;
                    Answerist.Add(string.Format("{0} {1} {2} {3}", LoopX, LoopY, LoopX + 1, LoopY));
                }
                if (BoolArr[LoopX, LoopY] && BoolArr[LoopX - 1, LoopY + 1]) {
                    BoolArr[LoopX, LoopY] = false;
                    BoolArr[LoopX - 1, LoopY + 1] = false;
                    Answerist.Add(string.Format("{0} {1} {2} {3}", LoopX, LoopY, LoopX - 1, LoopY + 1));
                }
                if (BoolArr[LoopX, LoopY] && BoolArr[LoopX, LoopY + 1]) {
                    BoolArr[LoopX, LoopY] = false;
                    BoolArr[LoopX, LoopY + 1] = false;
                    Answerist.Add(string.Format("{0} {1} {2} {3}", LoopX, LoopY, LoopX, LoopY + 1));
                }
            }
        }
        Console.WriteLine(Answerist.Count);
        Answerist.ForEach(pX => Console.WriteLine(pX));
    }
}

解説

ネクタリスのHex座標を意識します。

するとZオーダーでマス目を見ていき、
●自マスと右マス
●自マスと左下マス
●自マスと右下マス
をこの順で優先しつつ、選択すれば良いと分かります。