Counting Instances of a Character in a String

[Signit]

I am trying to count the number of semicolons ; in a string. I have tried a variety of methods to no avail in that each way I have tried I only get the length of the string returned.

// one attempted method
for (int i = 0; i < v_myIngredients.Length; i++)
{
  if(String.Equals(v_myIngredients.Substring(v_myIngredients.IndexOf(";")),";"))
  {
    listCount++;
  }
}

// other attempted method
for (int i = 0; i < v_myIngredients.Length; i++)
{
  if(v_myIngredients.Substring(v_myIngredients.IndexOf(";")==";"))
  {
    listCount++;
  }
}

Neither way has worked. Any suggestions would be apprecaited. I think it might be because I am just comparing objects of type eg IF sees both as being characters so therefore it says it's true and moves on.

 

[crazyboybert]

You can use RegularExpressions for this. you will need to import the System.Text.RegularExpression namespace.

Regex r = new Regex(";");
MatchCollection mc = r.Matches(stringToMatch);
int matches = mc.Count;

Hope this helps

Rob

Go placidly amidst the noise and haste, and remember what peace there may be in silence - Erhmann 1927

 

[Signit]

Thanks for the tip. I ended up doing this this morning:

for (int i = 0; i < v_myIngredients.Length; i++)
{
  if(v_myIngredients.Substring(i,1)==";")
  {
    listCount++;
  }
}

 

[kneejnick]

that is faster isn't it?

 

[obislavu]

The above function is working but no so performant.
Here is improved one:

public int CountOcc2(string s, char ch)
{   int iCount=0;
    for (int i=0;i<s.Length;i++)
	{
	   if (s[i]==ch) 
		iCount++;
	}
    return iCount;
}

int count1=CountOcc2("a;blabla;ccccc;d",';');

-obislavu-

 

[chiph]

obislavu -

This is an unusual case, but it is possible for it to happen: the string may contain a Unicode surrogate character. When it does, using an indexer to go through the string is likely to fail. In that case, you'll want to do something like this:

public int CountOcc3(string s, char ch)
{
   int iCount=0;
   CharEnumerator ce = s.GetEnumerator();
   while (ce.MoveNext())
   {
      if (ce.Current == ch)
        iCount++;
   }
   return iCount;
}

Chip H.


If you want to get the best response to a question, please check out FAQ222-2244 first

 

[cappmgr]

My vote goes to the Regex from crazyboybert.
Marty

 

[octothorpe]

int count = foo.Length - foo.Replace( ";", "" );

That should work too, but I don't know what solution runs the fastest.

 

[octothorpe]

Correction:

int count = foo.Length - foo.Replace( ";", "" ).Length;