using System;

using System.Linq;

using System.Collections.Generic;

using System.Collections;

​

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

        TreeItem a111 = new TreeItem("a111");

        TreeItem a11 = new TreeItem("a11", new List<TreeItem>{a111});

        TreeItem a12 = new TreeItem("a12");

        TreeItem a1 = new TreeItem("a1", new List<TreeItem>{a11, a12});

        TreeItem b111 = new TreeItem("b111");

        TreeItem b11 = new TreeItem("b11", new List<TreeItem>{b111});

        TreeItem b12 = new TreeItem("b12");

        TreeItem b1 = new TreeItem("b1", new List<TreeItem>{b11, b12});

        // Test 1

        Console.WriteLine("===== Test 1 =====");

        a1.IsShowAlternateColor = false;

        RunTest(new List<TreeItem> {a1, b1}, a1, new List<Tuple<string, bool>>

        {

            Tuple.Create("a1", false),

            Tuple.Create("a11", true),

            Tuple.Create("a111", false),

            Tuple.Create("a12", true),

            Tuple.Create("b1", false),

            Tuple.Create("b11", true),

            Tuple.Create("b111", false),

            Tuple.Create("b12", true),

        });

​

        // Test 2       

        Console.WriteLine("===== Test 2 =====");

        a11.IsExpanded = false;

        RunTest(new List<TreeItem> {a1, b1}, a11, new List<Tuple<string, bool>>

        {

            Tuple.Create("a1", false),

            Tuple.Create("a11", true),

            Tuple.Create("a111", false),

            Tuple.Create("a12", false),

            Tuple.Create("b1", true),

            Tuple.Create("b11", false),

            Tuple.Create("b111", true),

            Tuple.Create("b12", false),

        });

        // Test 3

        Console.WriteLine("===== Test 3 =====");

        b11.IsExpanded = false;

        RunTest(new List<TreeItem> {a1, b1}, a1, new List<Tuple<string, bool>>

        {

            Tuple.Create("a1", false),

            Tuple.Create("a11", true),

            Tuple.Create("a111", false),

            Tuple.Create("a12", false),

            Tuple.Create("b1", true),

            Tuple.Create("b11", false),

            Tuple.Create("b111", true),

            Tuple.Create("b12", true),

        });

    }

​

​

    public static void RunTest(IEnumerable<TreeItem> treeItems, TreeItem modifiedTreeItem, IEnumerable<Tuple<string, bool>> expectedResults)

    {

        AlternateColorSetter target = new AlternateColorSetter(treeItems);

        target.Start(modifiedTreeItem);

        List<Tuple<string, bool>> actuals = new List<Tuple<string, bool>>();

        Program.Iterate(actuals, treeItems);

        if(actuals.Count() != expectedResults.Count())

        {

            throw new Exception("The number of elements was wrong.");

        }

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

        {

            if(actuals.ElementAt(i).Item1 != expectedResults.ElementAt(i).Item1)

            {

                throw new Exception("The " + (i + 1) + "th element has a wrong id.");

            }

            if(actuals.ElementAt(i).Item2 != expectedResults.ElementAt(i).Item2)

            {

                throw new Exception("The " + (i + 1) + "th element has a wrong alternate color setting.");

            }

        }

        Console.WriteLine("Test passed");

    }

    private static void Iterate(List<Tuple<string, bool>> actuals, IEnumerable<TreeItem> treeItems)

    {

        foreach (TreeItem treeItem in treeItems)

        {

            actuals.Add(Tuple.Create(treeItem.Id, treeItem.IsShowAlternateColor));

            Program.Iterate(actuals, treeItem.GetChildren());

        }

    }

    public class AlternateColorSetter

    {

        private bool isStartingTreeItemLocated = false;

        private TreeItem startingTreeItem = null;

        private bool isShowAlternateColor = false;

        private IEnumerable<TreeItem> treeItems;

        public AlternateColorSetter(IEnumerable<TreeItem> treeItems)

        {

            this.treeItems = treeItems;

        }

        public void Start(TreeItem startingTreeItem)

        {

            this.isStartingTreeItemLocated = false;

            this.startingTreeItem = startingTreeItem;

            this.Iterate(this.treeItems);

        }

        private void Iterate(IEnumerable<TreeItem> treeItems)

        {

            foreach (TreeItem treeItem in treeItems)

            {

                if (!this.isStartingTreeItemLocated)

                {

                    this.isStartingTreeItemLocated = treeItem == this.startingTreeItem;

                    if(this.isStartingTreeItemLocated)

                    {

                        this.isShowAlternateColor = treeItem.IsShowAlternateColor;

                    }

                    if(treeItem.IsExpanded)

                    {

                        this.Iterate(treeItem.GetChildren());

                    }

                }

                else

                {

                    treeItem.IsShowAlternateColor = !this.isShowAlternateColor;

                    this.isShowAlternateColor = treeItem.IsShowAlternateColor;

                    if(treeItem.IsExpanded)

                    {

                        this.Iterate(treeItem.GetChildren());

                    }

                }

            }

        }

    }

    public class TreeItem

    {

        public IEnumerable<TreeItem> Children {get; private set; }

        public string Id {get; private set;}

        public TreeItem(string id, IEnumerable<TreeItem> children)

        {

            this.Id = id;

            this.Children = children;

            this.IsExpanded = true;

        }

        public TreeItem(string id)

        {

            this.Id = id;

            this.Children = new List<TreeItem>();

            this.IsExpanded = true;

        }

        public IEnumerable<TreeItem> GetChildren()

        {

            return this.Children;

        }

        public bool IsShowAlternateColor { get; set; }

        public bool IsExpanded {get; set;}

    }

}