Encoding the string length of a given string

Question

Enter the code for the run -length encoding of the given string.
Sample input: aaaaaaaaaabcccccc
Output: a10bc6

My code is:

static void Main(string[] args)
{
    string str = "aaaaaaaaaabcccccc";
    var qry = (from c in str
               group c by c into grp
               select new
               {
                   output = grp.Key.ToString() + grp.Count().ToString()
               });
    StringBuilder sb = new StringBuilder();
    foreach (var item in qry)
    {
        sb.Append(item.output);
    }
    Console.WriteLine(sb.ToString());
    Console.ReadLine();
}

However, it returns:

a10b1c6

I want to delete the counter for a non-repeating char, here is a "1" for the letter "b".

Suppose this is a sorted string.

Answer 1

Here's a simplified version:

public static void Main()
{
   string str = "aaaaaaaaaabcccccc";
    var qry = (from c in str
               group c by c into grp
               let c = grp.Count()
               select grp.Key.ToString() + (c > 1 ? c.ToString() : ""));

    Console.WriteLine(string.Join("",qry));
    Console.ReadLine();
}

You need to be careful with placing the brackets around the triple expression, and then I used string.Jointo avoid mess with the loop for eachand line builder.

Answer 2

add ternary expression:

output = grp.Key + (grp.Count() > 1 ? grp.Count().ToString() : "")

Answer 3

OP , / , , Run Length encoding , . :

  string str = "aaaaaaaabccccccaadddddaaa"; // a8bc6a2d5a3

  // Zip the string with itself, offset by 1 character. 
  // Duplicate the last char to make strings equal length
  var pairs = str
    .Zip((str + str.Last()).Skip(1),
         (prev, current) => new { prev, current });

  // Retain a horrid mutable sequence which tracks consecutive characters
  var sequence = 0;
  var grps = pairs.GroupBy(p => 
    new { Ch = p.prev, 
          Sequence = p.current == p.prev
          ? sequence 
          : sequence++});

  // Join this together, using the other solutions to drop the count from single chars
  var rle = String.Join("", 
    grps.Select(g => g.Count() > 1
        ? g.Key.Ch.ToString() + g.Count().ToString() 
        : g.Key.Ch.ToString()));
  Console.WriteLine(rle);

Edit
, POLA, :

• Zip (Skip),
• Zip , .
• "" RLE , , " "? .
• lambda GroupBy
• @Jonesy/@Tim String.Join .

Answer 4

. - Lookup, String.Concat:

var charLook = input.ToLookup(c => c);
string result = string.Concat(charLook
    .Select(g => string.Format("{0}{1}", g.Key, g.Count()==1 ? "" : g.Count().ToString())));

Answer 5

, , :

StringBuilder sb = new StringBuilder();
string x = "aaaaaaaaaabcccccc";
char[] c = x.ToCharArray();
char[] t = c.Distinct().ToArray();
for (int i = 0; i < t.Length; i++)
{
   int count = 0;

   for (int j = 1; j < c.Length; j++)
   {  
       if (t[i] == c[j - 1])
       {
          count++;
       }
   }

   if (count > 1)
   {
       sb.Append(t[i] + count.ToString());
   }
   else
   {
       sb.Append(t[i]);
   }

}
Console.Write(sb);
Console.ReadKey();