How to find total count of a character in a string

[john20]

Hi All,

How can i find the total 'Count' of a particular character's occurance in a string.

means i want to find the count of '<' in a string.

can you please help to find that.

Thanks

[Plater]

So if you had the string: "fred<ran<fast<" and looking for count of "<"
You would want the number 3 to be returned?
I think a regex can do this, you tell it to match that character and return a set of matches, and the number of matches will tell you the number of occurances?

[Curtis Rutland]

Well, if you want to keep things simple...

String has a ToCharArray method. Use it, then loop through the array, incrementing a counter every time that you encounter the specific char.

string CountCharInstances(string s, char c)
{
  char[] ch = s.ToCharArray();
  int count = 0;
  for(int i=0; i<ch.Length; i++)
    if(ch[i] == c)
      count++;
  return count;
}

[balabaster]

I way prefer regex for this. I'll use Plater's test string as InputString, and ">" as my SearchString variable.

int Count = Regex.Matches(InputString, SearchString).Count;

But a simple split would also suffice:

int Count = InputString.Split(SearchString).Count - 1;

[Curtis Rutland]

I don't think that split will work, if the character starts or ends the string. But the Regex answer is much more elegant than mine.

[Plater]

Yes, I don't normally suggest a regex right off, but if the input string was thousands and thousands of characters, iterating through manually would be tedious.

[balabaster]

@insertAlias
Well in the tests I ran it works in both cases. I used the following SearchString: "<fred<ran<fast<<<"

Split.Count - 1 provided the same result as Regex.Match.Count

Obviously you need to take into account that the purpose of split is to find the strings between the chars and not the chars themselves. But handily [is that a word?], in cases where you've got adjacent search characters it provides "" as the string between them in the array. So you'll always end up with n+1 where n is the value you're looking for.

So in cases where you don't fully understand Regex - split will work nicely as a "dirty but elegant" solution - if such a thing could exist.

[balabaster]

@Plater
How does the anecdote go? Sometimes you'll have a problem and you think "I know, I'll use a regular expression". Now you've got two problems...

[balabaster]

You could also do it with LINQ:

int Count = InputString.Where(c => c = SearchString).Count;

It doesn't perform as well as regex or split though, so while it's amusing to come up with as many variant ways of performing this task with minimal code, it's probably not the choice to use in this case.

You could just do a plain old count using a predicate. This one actually appears to perform as well as split and regex and is probably the right way to go. It is more intuitive to someone reading your code as to what it's purpose is at a glance:

int Count = InputString.Count(CurrentChar => CurrentChar = SearchChar);

Another dirty but performant solution:

int Count = InputString.Length - InputString.Replace(SearchString, String.Empty).Length;

[Curtis Rutland]

OK, I didn't realize that Split returned empty strings by default, good stuff to know.