using System;

using System.Collections.Generic;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        var abc = new List<string>{"a", "b", "c"};

        var xyz = new List<string>{"x", "y", "z"};

        var braidedArray = BraidArrays(new List<List<string>>{abc, xyz});

        Console.WriteLine(string.Join(",", braidedArray));

        // BraidArrays works for any number of arrays. Feel free to uncomment these lines to see it in action combining 3 arrays:

        // var oneTwoThree = new List<string>{"1", "2", "3"};

        // var braidedArrayTwo = BraidArrays(new List<List<string>>{abc, xyz, oneTwoThree});

        // Console.WriteLine(string.Join(",", braidedArrayTwo));

    }

​

    private static List<T> BraidArrays<T>(List<List<T>> lists)

    {

        // declare our braided list we are about to build

        var braided = new List<T>{};

        // find the length of the longest list - project the length then call Max() to find it

        var longestListLength = lists.Select(x => x.Count).Max();

        // will  need to loop for the longest list

        for (var i = 0; i < longestListLength; i++)

        {

            // take the value at each index in order (if it exists)

            foreach (var list in lists)

            {

                if (list.ElementAtOrDefault(i) != null)

                {

                    braided.Add(list[i]);

                }

            }

        }

​

        // return the list!

        return braided;

    }

}