仅使用正则表达式匹配罗马数字

Question

I'm trying to create a reg exp to match only roman numerals, and remove them only when there are other characters before. If there are not other characters before the roman numeral then I don't want to remove it. Here is an example:

string1 V
string2 VI
string3 XX
STRING4 I
STRING5 1340 I
2 STRING6 III
STRING7 V
STRING8 III
STRING9 II
STRING10 IV
STRING11 STRING12 VI
STRING13! IX
STRING14 VI
. STRING15 - STRING16_ V
STRING17 1/2 VI
STRING18 VIII
XIII (2011)
V (2012)
String19 VP
XII

the result should be:

string1
string2
string3
STRING4
STRING5 1340
2 STRING6
STRING7
STRING8
STRING9
STRING10
STRING11 STRING12
STRING13!
STRING14
. STRING15 - STRING16_
STRING17 1/2
STRING18
XIII (2011)
V (2012)
String19 VP
XII

Any help please?

Thanks

edit : I have just tried this: \\b[IVXLCDM]+\\b but it matches:

XIII (2011)
V (2012)
XII

Answer 1

You can use [ ]\\bM{0,4}(CM|CD|D?C{0,3})(XC|XL|L?X{0,3})(IX|IV|V?I{0,3})\\b

Includes only valid ROMAN NUMERALS.

If you want to include romans without validation you can use [ ]([MDCLXVI]+$)

see DEMO .

Answer 2

<?php

$subjects = <<< EOT
string1 V
string2 VI
string3 XX
STRING4 I
STRING5 1340 I
2 STRING6 III
STRING7 V
STRING8 III
STRING9 II
STRING10 IV
STRING11 STRING12 VI
STRING13! IX
STRING14 VI
. STRING15 - STRING16_ V
STRING17 1/2 VI
STRING18 VIII
XIII (2011)
V (2012)
String19 VP
XII
EOT;

foreach (explode("\n",$subjects) as $subject) {
  $pattern = '/(.+)\s+[IVXLCDM]+\s*$/';
  echo preg_replace($pattern, '\\1', $subject)."\n";
}

This gives the output:

string1
string2
string3
STRING4
STRING5 1340
2 STRING6
STRING7
STRING8
STRING9
STRING10
STRING11 STRING12
STRING13!
STRING14
. STRING15 - STRING16_
STRING17 1/2
STRING18
XIII (2011)
V (2012)
String19 VP
XII

Note: this also removes any white spaces between the preceding text and the removed roman number sequence. If you want to preserve those you have to move the \\n into the brackets before: '/(.+\\s+)[CILMVX]+$/' .