C#

string laceStrings(const string& s1, const string& s2)
{
    if (s1.empty())
        return s2;
    if (s2.empty())
        return s1;

    string laced;
    laced.resize(s1.size() + s2.size());

    int i = 0, pos = 0;
    int size = std::min(s1.size(), s2.size());

    // interlace common lengths substrings
    for ( ; i < size; ++i)
    {
        laced[pos++] = s1[i];
        laced[pos++] = s2[i];
    }

    // append the remainder of longer string
    if (s1.size() >= s2.size())
        for ( ; i < s1.size(); ++i)
            laced[pos++] = s1[i];
    else
        for ( ; i < s2.size(); ++i)
            laced[pos++] = s2[i];

    return laced;
}

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

namespace ConsoleApplication2
{
    class Program
    {
        static void Main(string[] args)
        {

            List<DateTime> dtArray1 = new List<DateTime>();
            List<DateTime> dtArray2 = new List<DateTime>();


            Console.WriteLine("START Enter date");

            for (int i = 0; i <= 2; i++)
            {
                string sStartdate1 = string.Empty;
                sStartdate1 = Console.ReadLine();


                DateTime dStartDate1;
                if (DateTime.TryParse(sStartdate1, out dStartDate1))
                {
                    dtArray1.Add(dStartDate1);
                }
            }

            foreach (var item in dtArray1)
            {
                Console.WriteLine(item);
            }

            Console.ReadLine();


            Console.WriteLine("end Enter date");

            for (int j = 0; j <= 2; j++)
            {
                string sStartdate2 = string.Empty;
                sStartdate2 = Console.ReadLine();


                DateTime dStartDate2;
                if (DateTime.TryParse(sStartdate2, out dStartDate2))
                {
                    dtArray2.Add(dStartDate2);
                }
            }

            foreach (var item in dtArray2)
            {
                Console.WriteLine(item);
            }

            Console.ReadLine();



           
        }

        }
    }


/*here i enter array yes? know i want compare this array like this    1990|---------|2000
             here 1990,1995 is dtArray1,2000,20005 dtArray2                 1995|-------|2005
                                                                            1995|-------|2005

 my result should be 2000-1990+2005-2000= 15  my year without intersection is 15.*/