[boost] [regex] Change format of data in file

Subject: [boost] [regex] Change format of data in file
From: Fu ji (fujimailing_at_[hidden])
Date: 2015-04-26 11:06:13

Hello all,
I have file output.txt, in file we can find something like:

01/01/2015 15:00:00 2222.2222

2222.2222 2222.2222 2222.2222

04/04/2015 15:00:00 2222.2222

and i would like to change format from DD/MM/RRRR HH:MM:SS to RRRR-MM-DD
HH:MM:SS.000 using boost regex. But I have no clue how should I type
pattern and replace them with another.

Anyone have knowledge about boost regex and could help me ?

Best regards