Separate title string with no spaces into words

Question

I want to find and separate words in a title that has no spaces.

Before:

ThisIsAnExampleTitleHELLO-WORLD2019T.E.S.T.(Test)"Test"'Test'[Test]

After:

This Is An Example Title HELLO-WORLD 2019 T.E.S.T. (Test) [Test] "Test" 'Test'

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I'm looking for a regular expression rule that can do the following.

I thought I'd identify each word if it starts with an uppercase letter.

But also preserve all uppercase words as not to space them into A L L U P P E R C A S E.

Additional rules:

• Space a letter if it touches a number: Hello2019World Hello 2019 World
• Ignore spacing initials that contain periods, hyphens, or underscores T.E.S.T.
• Ignore spacing if between brackets, parentheses, or quotes [Test] (Test) "Test" 'Test'
• Preserve hyphens Hello-World

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C#

https://rextester.com/GAZJS38767

// Title without spaces string title = "ThisIsAnExampleTitleHELLO-WORLD2019T.E.S.T.(Test)[Test]\"Test\"'Test'";  // Detect where to space words string[] split =  Regex.Split(title, "(?<!^)(?=(?<![.\\-'\"([{])[A-Z][\\d+]?)");  // Trim each word of extra spaces before joining split = (from e in split          select e.Trim()).ToArray();  // Join into new title string newtitle = string.Join(" ", split);  // Display Console.WriteLine(newtitle); 

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Regular expression

I'm having trouble with spacing before the numbers, brackets, parentheses, and quotes.

https://regex101.com/r/9IIYGX/1

(?<!^)(?=(?<![.\-'"([{])(?<![A-Z])[A-Z][\d+?]?)  (?<!^)          // Negative look behind  (?=             // Positive look ahead  (?<![.\-'"([{]) // Ignore if starts with punctuation (?<![A-Z])      // Ignore if starts with double Uppercase letter [A-Z]           // Space after each Uppercase letter [\d+]?          // Space after number  ) 

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Solution

Thanks for all your combined effort in answers. Here's a Regex example. I'm applying this to file names and have exclude special characters \/:*?"<>|.

https://rextester.com/FYEVE73725

https://regex101.com/r/xi8L4z/1

Answer 1

Here is a regex which seems to work well, at least for your sample input:

(?<=[a-z])(?=[A-Z])|(?<=[0-9])(?=[A-Za-z])|(?<=[A-Za-z])(?=[0-9])|(?<=\W)(?=\W) 

This patten says to make a split on a boundary of one of the following conditions:

• what precedes is a lowercase, and what precedes is an uppercase (or vice-versa)
• what precedes is a digit and what follows is a letter (or vice-versa)
• what precedes and what follows is a non word character (e.g. quote, parenthesis, etc.)

string title = "ThisIsAnExampleTitleHELLO-WORLD2019T.E.S.T.(Test)[Test]\"Test\"'Test'"; string[] split =  Regex.Split(title, "(?<=[a-z])(?=[A-Z])|(?<=[0-9])(?=[A-Za-z])|(?<=[A-Za-z])(?=[0-9])|(?<=\\W)(?=\\W)");  split = (from e in split select e.Trim()).ToArray(); string newtitle = string.Join(" ", split);  This Is An Example Title HELLO-WORLD 2019 T.E.S.T. (Test) [Test] "Test" 'Test' 

Note: You might also want to add this assertion to the regex alternation:

(?<=\W)(?=\w)|(?<=\w)(?=\W) 

We got away with this here, because this boundary condition never happened. But you might need it with other inputs.