loop through string to find substring

Question

I have this string:

text = "book//title//page/section/para";

I want to go through it to find all // and / and their index.

I tried doing this with:

if (text.Contains("//"))
{
    Console.WriteLine(" // index:  {0}  ", text.IndexOf("//"));   
}
if (text.Contains("/"))
{
    Console.WriteLine("/ index:  {0}  :", text.IndexOf("/"));    
}

I was also thinking about using:

Foreach(char c in text)

but it will not work since // is not a single char.

How can I achieve what I want?

I tried this one also but did not display result

string input = "book//title//page/section/para"; 
string pattern = @"\/\//";


Regex rgx = new Regex(pattern, RegexOptions.IgnoreCase);
MatchCollection matches = rgx.Matches(input);
 if (matches.Count > 0)
  {
      Console.WriteLine("{0} ({1} matches):", input, matches.Count);
      foreach (Match match in matches)
         Console.WriteLine("   " + input.IndexOf(match.Value));
 }

Thank you in advance.

What is the expected output for ///? {0}? {0, 1}? Something else? — Ani
– Ani, Commented Jan 19, 2011 at 3:43
I cleaned up the code formatting, grammar, and punctuation a bit in hopes of making it easier to understand. — Redwood
– Redwood, Commented Jan 19, 2011 at 3:49
I have tried this but does not work string input = "book//title//page/section/para"; string pattern = @"\/\//"; Regex rgx = new Regex(pattern, RegexOptions.IgnoreCase); MatchCollection matches = rgx.Matches(input); if (matches.Count > 0) { Console.WriteLine("{0} ({1} matches):", input, matches.Count); foreach (Match match in matches) Console.WriteLine(" " + input.IndexOf(match.Value)); } — Dena
– Dena, Commented Jan 19, 2011 at 4:02

Timwi · Accepted Answer · 2011-01-19 04:02:13Z

9

Simple:

var text = "book//title//page/section/para";
foreach (Match m in Regex.Matches(text, "//?"))
    Console.WriteLine(string.Format("Found {0} at index {1}.", m.Value, m.Index));

Output:

Found // at index 4.
Found // at index 11.
Found / at index 17.
Found / at index 25.

answered Jan 19, 2011 at 4:02

Timwi

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Comments

Craig · Accepted Answer · 2011-01-19 03:43:41Z

4

Would it be possible using Split?

So:

string[] words = text.Split(@'/');

And then go through the words? You would have blanks, due to the //, but that might be possible?

answered Jan 19, 2011 at 3:43

Craig

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2 Comments

Matt Hamilton Over a year ago

You can use StringSplitOptions.RemoveEmptyEntries so you don't get blanks, too.

cHao Over a year ago

In this case, you might want the blanks. Every blank (that's not the first or last in the array) will be between a pair of slashes.

JamesF · Accepted Answer · 2011-01-19 03:52:10Z

2

If what you want is a list "book","title","page","section","para" you can use split.

    string text = "book//title//page/section/para";
    string[] delimiters = { "//", "/" };

    string[] result = text.Split(delimiters,StringSplitOptions.RemoveEmptyEntries);
    System.Diagnostics.Debug.WriteLine(result);
    Assert.IsTrue(result[0].isEqual("book"));
    Assert.IsTrue(result[1].isEqual("title"));
    Assert.IsTrue(result[2].isEqual("page"));
    Assert.IsTrue(result[3].isEqual("section"));
    Assert.IsTrue(result[4].isEqual("para"));

answered Jan 19, 2011 at 3:52

JamesF

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1 Comment

Dena Over a year ago

Actually what I need is not book,title,..so on .. I need / and // and its positions

Neil · Accepted Answer · 2011-01-19 03:51:48Z

1

Sometin like:

bool lastCharASlash = false;
foreach(char c in text)
{
    if(c == @'/')
    {
      if(lastCharASlash)
      { 

          // my code...
      }
      lastCharASlash = true;
    }
    else lastCharASlash = false;
}

You can also do text.Split(@"//")

answered Jan 19, 2011 at 3:51

Neil

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1 Comment

Neil Over a year ago

Timwi's regex is probably the better way to do this.

Divi · Accepted Answer · 2011-01-19 04:46:49Z

-2

You could replace // and / with your own words and then find the last index of

string s = "book//title//page/section/para";

        s = s.Replace("//", "DOUBLE");
        s = s.Replace("/", "SINGLE");

        IList<int> doubleIndex = new List<int>();

        while (s.Contains("DOUBLE"))
        {
            int index = s.IndexOf("DOUBLE");
            s = s.Remove(index, 6);
            s = s.Insert(index, "//");
            doubleIndex.Add(index);
        }

        IList<int> singleIndex = new List<int>();

        while (s.Contains("SINGLE"))
        {
            int index = s.IndexOf("SINGLE");
            s = s.Remove(index, 6);
            s = s.Insert(index, "/");
            singleIndex.Add(index);
        }

Remember to first replace double, otherwise you'll get SINGLESINGLE for // instead of DOUBLE. Hope this helps.

edited Jan 19, 2011 at 4:46

answered Jan 19, 2011 at 3:58

Divi

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4 Comments

cHao Over a year ago

This would go pretty badly if the text were, say, "/SINGLE//SINGLE/DOUBLE/".

Divi Over a year ago

Agreed. Didn't think of that. I guess you could use regex

Dena Over a year ago

no it is good point since this will be bookdDOUBLEtitleDouble...etc but still the problem has not been solved which this will not loop to check all time of Double and Single appear in the text

Divi Over a year ago

Sorry didn't realise you wanted all indexes. I've update the code above to reflect your solution. It could be done in a cleaner way, but it gives you an idea.

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