CGL_2_A: Parallel/Orthogonal

問題へのリンク

C#のソース

using System;
using System.Collections.Generic;
using System.Linq;

// Q058 線分の平行と垂直の判定 https://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=CGL_2_A&lang=jp
class Program
{
    static string InputPattern = "Input1";

    static List<string> GetInputList()
    {
        var WillReturn = new List<string>();

        if (InputPattern == "Input1") {
            WillReturn.Add("3");
            WillReturn.Add("0 0 3 0 0 2 3 2");
            WillReturn.Add("0 0 3 0 1 1 1 4");
            WillReturn.Add("0 0 3 0 1 1 2 2");
            //2
            //1
            //0
        }
        else {
            string wkStr;
            while ((wkStr = Console.ReadLine()) != null) WillReturn.Add(wkStr);
        }
        return WillReturn;
    }

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

        int[] wkArr = { };
        Action<string> SplitAct = pStr =>
            wkArr = pStr.Split(' ').Select(X => int.Parse(X)).ToArray();

        foreach (string EachStr in InputList.Skip(1)) {
            SplitAct(EachStr);
            int X0 = wkArr[0];
            int Y0 = wkArr[1];
            int X1 = wkArr[2];
            int Y1 = wkArr[3];

            int X2 = wkArr[4];
            int Y2 = wkArr[5];
            int X3 = wkArr[6];
            int Y4 = wkArr[7];

            Solve(X0, Y0, X1, Y1, X2, Y2, X3, Y4);
        }
    }

    static void Solve(int pX0, int pY0, int pX1, int pY1, int pX2, int pY2, int pX3, int pY3)
    {
        // 原点が始点になるように平行移動し、ベクトルで考える
        int Vector1_X = pX1 - pX0;
        int Vector1_Y = pY1 - pY0;

        int Vector2_X = pX3 - pX2;
        int Vector2_Y = pY3 - pY2;

        // 内積が0なら 垂直
        bool IsVertical = (Vector1_X * Vector2_X + Vector1_Y * Vector2_Y == 0);

        // a1b2 - a2b1 = 0 なら平行
        bool IsParallel = (Vector1_X * Vector2_Y - Vector1_Y * Vector2_X == 0);

        if (IsParallel) {
            Console.WriteLine(2);
        }
        else if (IsVertical) {
            Console.WriteLine(1);
        }
        else {
            Console.WriteLine(0);
        }
    }
}

解説

外積と内積を使って、判定してます。