Question

How can I convert the string russ(ai)(edocn)cup to russiancodecup using Ruby?

Answer 1

By using gsub with a block, you can replace any match of a regular expression by the result of this block.

s = "russ(ai)(edocn)cup"
s.gsub(/\(([^)]*)\)/) {$1.reverse}  # => "russiancodecup"

Here the regular expression will match any non-) character between brackets. Then it will send reverse to $1 which is gonna be the content between brackets.

$0 will be the complete match and $n, the nth “submatch”. (anybody for the correct word ?)