Most relevant passage retrieval

I need to write an algorithm to retrieve most relevant passage from a
large body of text. The passage needs to relevant to the search term.
Sort of like what Google displays on their search results page as the
summary of the page. Thanks in advance.

sysindex wrote:[color=blue]
> I need to write an algorithm to retrieve most relevant passage from a
> large body of text. The passage needs to relevant to the search term.
> Sort of like what Google displays on their search results page as the
> summary of the page. Thanks in advance.[/color]

What does it have to do with C++ language? Display three words
before the word you find and three words after, you'll get your
"passage".