How to split a string into an array of two letter substrings with C#

Question

Problem

Given a sample string abcdef, i am trying to split that into an array of two character string elements that should results in ['ab','cd','ef'];

What i tried

I tried to iterate through the string while storing the substring in the current index in an array i declared inside the method, but am getting this output ['ab','bc','cd','de','ef']

Code I used

static string[] mymethod(string str)
{
    string[] r= new string[str.Length];
    for(int i=0; i<str.Length-1; i++)
    {
        r[i]=str.Substring(i,2);
    }
    return r;
}

Any solution to correct that with the code to return the correct output is really welcome, Thanks

Answer 1

your problem was that you incremented your index by 1 instead of 2 every time

 var res = new List<string>();
 for (int i = 0; i < x.Length - 1; i += 2)
 {
     res.Add(x.Substring(i, 2));
 }

should work

EDIT: because you ask for a default _ suffix in case of odd characters amount, this should be the change:

  var testString = "odd";
  string workOn = testString.Length % 2 != 0
     ? testString + "_"
     : testString;
  var res = new List<string>();
  for (int i = 0; i < workOn.Length - 1; i += 2)
  {
      res.Add(workOn.Substring(i, 2));
  }

two notes to notice:

• in .NET 6 Chunk() is available so you can use this as suggested in other answers
• this solution might not be the best in case of a very long input so it really depends on what are your inputs and expectations

Answer 2

.net 6 has an IEnumerable.Chunk() method that you can use to do this, as follows:

public static void Main()
{
    string[] result = 
       "abcdef"
       .Chunk(2)
       .Select(chunk => new string(chunk)).ToArray();

    Console.WriteLine(string.Join(", ", result)); // Prints "ab, cd, ef"
}

Before .net 6, you can use MoreLinq.Batch() to do the same thing.

---

[EDIT] In response the the request below:

MoreLinq is a set of Linq utilities originally written by Jon Skeet. You can find an implementation by going to Project | Manage NuGet Packages and then browsing for MoreLinq and installing it.

After installing it, add using MoreLinq.Extensions; and then you'll be able to use the MoreLinq.Batch extension like so:

public static void Main()
{
    string[] result = "abcdef"
       .Batch(2)
       .Select(chunk => new string(chunk.ToArray())).ToArray();

    Console.WriteLine(string.Join(", ", result)); // Prints "ab, cd, ef"
}

Note that there is no string constructor that accepts an IEnumerable<char>, hence the need for the chunk.ToArray() above.

I would say, though, that including the whole of MoreLinq just for one extension method is perhaps overkill. You could just write your own extension method for Enumerable.Chunk():

public static class MyBatch
{
    public static IEnumerable<T[]> Chunk<T>(this IEnumerable<T> self, int size)
    {
        T[] bucket = null;
        int count  = 0;

        foreach (var item in self)
        {
            if (bucket == null)
                bucket = new T[size];

            bucket[count++] = item;

            if (count != size)
                continue;

            yield return bucket;

            bucket = null;
            count  = 0;
        }

        if (bucket != null && count > 0)
            yield return bucket.Take(count).ToArray();
    }
}