C# character counting in a string and add in a period in a string

This one开发者_StackOverflow is really simple but I'm just not sure how to do it without foreach looping over each line.

What I want to do is place a period (.) after the 6th character in each string.

Input:

ads234adf4234asd  
dfasd234asdf45  
rte3443  
fdf323ggt  
vgdfg767575  
sdgsdfgdfg756756    

Output:

ads234.adf4234asd  
dfasd2.34asdf45  
rte344.3  
fdf323.ggt  
vgdfg7.67575  
sdgsdf.gdfg756756

How can I do this?

---

For each string you can use string.Insert to get the result you want:

string s = "ads234adf4234asd";
s = s.Insert(6, ".");

If you want to avoid writing an explicit for loop you could try LINQ:

string[] result = lines
    .Select(s => s.Insert(6, "."))
    .ToArray();

Note that this avoids the foreach but it doesn't avoid looping - there's still a loop inside the implementation of Select.

If you don't want the program to crash if it receives a string of length 5 or less but just to return the string unchanged, then try this:

string[] result = lines
    .Select(s => s.Length >= 6 ? s.Insert(6, ".") : s)
    .ToArray();

---

The following RegEx will insert a . after the 6th character of each line:

Regex.Replace(yourInputString, "^(?<before>.{6})(?<after>.*)$", @"${before}.${after}", RegexOptions.Multiline);

---

You can use the modulus operator to achieve this. e.g.

string myString = "abcdefghijklmnopqrstuvwxyz";
string newString = "";
for (int i = 0; i < myString.Length; i++)
{
    if (i !=0 && i % 6 == 0)
    {
        newString += ".";
    }
    newString += myString[i];
}

---

I can't see a way of not looping at all -- if you have it stored as a single char array you could step through each char and insert a period 6 chars after each return/newline char you find.

edit: may have misunderstand foreach looping each line ... do you mean foreach looping from line to line, or looping through the chars in each line?

---

Well, if you divide the length of the string by 6 you know how many periods to add. So...

// -1 to account for i = 6 in the loop to start
int numPeriods = ( str.Length / 6 ) - 1;

// we increment the index by 7 to account for the period we added
for( int index = 6, i = 0; i < numPeriods; index += 7, ++i )
{
    str = str.Insert( index, "." );
}

I'm sure there is a more elegant way, but I have to get back to work!

Also, your written request and your example are not the same thing. You say

What I want to do is after every 6th character in a string place a '.'

But your example shows adding a period at index 6 for each line. Which is it?

---

I think that looping is the best way, maybe you could make your code cleaner with LINQ:

var linq = from text in strings
           where text.Length > 6
           select text.Insert(6, ".");

---

Untested, but t This might works:

string field = "ads234adf4234asd";

int i = 0;
while ((i += 6) < field.Length)
    field = field.Insert(i, ".");

Tested with corrections.

Or, if only after the 6th:

string field = "ads234adf4234asd";

if (field.Length >= 6)
    field = field.Insert(6, ".");

---

I'm going to reuse some code that I've presented previously that breaks an IEnumerable<T> into pages:

static class EnumerableExtensions {
    public static IEnumerable<IEnumerable<T>> GetPages<T>(
    this IEnumerable<T> source,
    int pageSize
) {
        var e = source.GetEnumerator();
        while (e.MoveNext()) {
            int count = pageSize - 1;
            List<T> list = new List<T>(pageSize) { e.Current };
            while (count > 0 && e.MoveNext()) {
                list.Add(e.Current);
                count--;
            }
            yield return list;
        }
    }
}

Then:

string s = "ads234adf4234asd";
var pages = s.GetPages(6);
string result = String.Join(".", pages.Select(a => new string(a.ToArray())));

Of course, there are loops buried in there which I can't really understand you wanting to avoid. However, if you really must avoid loops, you can do this recursively:

static string SplitAndInsert(string s, int afterEvery, char insertCharacter) {
        if (s.Length < afterEvery) {
            return s;
        }
        else {
            return 
                s.Substring(0, afterEvery) +
                insertCharacter +
                SplitAndInsert(
                    s.Substring(afterEvery, s.Length - afterEvery),
                    afterEvery,
                    insertCharacter
                );
        }
    }