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How to count words within a text string?

Answer 1

+3 A:

 [[stringToCOunt componentsSeparatedByCharactersInSet: [NSCharacterSet whitespaceCharacterSet] count]

ennuikiller 2010-02-15 14:16:49

`[[stringToCount componentsSeparatedByCharactersInSet:[NSCharacterSet whitespaceCharacterSet] count]`.

erikprice 2010-02-15 14:25:14

thanks erikprice for pointing out the oversight!

ennuikiller 2010-02-15 14:34:41

Fixed again.[[stringToCOunt componentsSeparatedByCharactersInSet: [NSCharacterSet whitespaceCharacterSet]] count]I was looking through documents by searching "counting words" or something like that, but I couldn't find a good way.This solution seems to be OK to me.Thank you all. (You guys are really quick!)

Nqeuew 2010-02-15 14:50:58

This is not the most efficient way to count words. Specially not memory wise since it will split the whole string into a temporary array that will then be discarded. It is much better to simply look at runs of whitespace and punctiation in the text. This can't be done in one line but it will be much faster and will not use at least double the memory of the text.

St3fan 2010-02-15 15:13:41

Answer 2

+3 A:

A more efficient method than splitting is to check the string character by character.

int word_count(NSString* s) {
  CFCharacterSetRef alpha = CFCharacterSetGetPredefined(kCFCharacterSetAlphaNumeric);
  CFStringInlineBuffer buf;
  CFIndex len = CFStringGetLength((CFStringRef)s);
  CFStringInitInlineBuffer((CFStringRef)s, &buf, CFRangeMake(0, len));
  UniChar c;
  CFIndex i = 0;
  int word_count = 0;
  Boolean was_alpha = false, is_alpha;
  while (c = CFStringGetCharacterFromInlineBuffer(&buf, i++)) {
    is_alpha = CFCharacterSetIsCharacterMember(alpha, c);
    if (!is_alpha && was_alpha)
      ++ word_count;
    was_alpha = is_alpha;
  }
  if (is_alpha)
    ++ word_count;
  return word_count;
}

Compared with @ennuikiller's solution, counting a 1,000,000-word string takes:

0.19 seconds to build the string
0.39 seconds to build the string + counting using my method.
1.34 seconds to build the string + counting using ennuikiller's method.

The big disadvantage of my method is that it's not a one-liner.

KennyTM 2010-02-15 15:05:05

not a one-liner is a bit of an understatement!! :) The op didn't ask for the most efficient solution. I would suspect that most methods in the NSString class can be coded more efficiently. I guess the determining factor would be how large the "text string" is.

ennuikiller 2010-02-16 13:25:37

Thanks Kenny! I was just asking a similar question and your answer is excellent! +1 ...i am gonna quietly borrow that code of yours.

Unikorn 2010-10-20 07:26:01

The solution is (slightly) broken. Not all characters fit in one unichar.

JeremyP 2010-10-20 09:03:10

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How to count words within a text string?

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