using System;

using System;

using System.Collections.Generic;

using System.Linq;

​

//[0.978982, 0.0, -0.20394638, 0.0],

//[0.20394637, 0.0, 0.97898203, 0.0],

//[-0.20394641, 0.0, -0.978982, 0.0], 

//[0.97898203, 0.0, -0.20394643, 0.0], 

​

​

public class Line {

    public int x1, y1, x2, y2;

​

    public Line(int x1, int y1, int x2, int y2) {

        this.x1 = x1;

        this.y1 = y1;

        this.x2 = x2;

        this.y2 = y2;

    }

​

    // todo lam tron

    public bool ConnectsTo(Line other) {

        return x1 == other.x2 && y1 == other.y2 || x2 == other.x1 && y2 == other.y1;

    }

}

​

public class LineGroupDetector {

    public List<List<Line>> DetectGroups(List<Line> lines) {

        Dictionary<Line, List<Line>> graph = BuildGraph(lines);

        List<List<Line>> groups = new List<List<Line>>();

        HashSet<Line> visited = new HashSet<Line>();

​

        foreach (Line line in lines) {

            if (!visited.Contains(line)) {

                List<Line> group = new List<Line>();

                TraverseGroup(line, graph, visited, group);

                groups.Add(group);

            }

        }

​

        return groups;

    }

​

    private Dictionary<Line, List<Line>> BuildGraph(List<Line> lines) {

        Dictionary<Line, List<Line>> graph = new Dictionary<Line, List<Line>>();

​

        foreach (Line line1 in lines) {

            foreach (Line line2 in lines) {

                if (line1 != line2 && line1.ConnectsTo(line2)) {

                    if (!graph.ContainsKey(line1)) {

                        graph[line1] = new List<Line>();

                    }

                    if (!graph.ContainsKey(line2)) {

                        graph[line2] = new List<Line>();

                    }

                    graph[line1].Add(line2);

                    graph[line2].Add(line1);

                }

            }

        }

​

        return graph;

    }

​

    private void TraverseGroup(Line line, Dictionary<Line, List<Line>> graph, HashSet<Line> visited, List<Line> group) {

        visited.Add(line);

        group.Add(line);

​

        foreach (Line neighbor in graph[line]) {

            if (!visited.Contains(neighbor)) {

                TraverseGroup(neighbor, graph, visited, group);

            }

        }

    }

}

​

public class Program

{

    public static void Main()

    {

        List<Line> lines = new List<Line>();

        lines.Add(new Line(0, 0, 1, 1));

        lines.Add(new Line(1, 1, 2, 2));

        lines.Add(new Line(3, 3, 4, 4));

        lines.Add(new Line(4, 4, 5, 5));

        lines.Add(new Line(5, 5, 6, 6));

        lines.Add(new Line(6, 6, 7, 7));

        lines.Add(new Line(8, 8, 9, 9));

        lines.Add(new Line(9, 9, 8, 8));

​

        LineGroupDetector detector = new LineGroupDetector();

        List<List<Line>> groups = detector.DetectGroups(lines);

​

        for (int i = 0; i < groups.Count; i++) {

            Console.WriteLine("Group " + (i + 1));

            foreach (Line line in groups[i]) {

                Console.WriteLine("(" + line.x1 + ", " + line.y1 + ") to (" + line.x2 + ", " + line.y2 + ")");

            }

            Console.WriteLine();

        }

    }

​

}