Regular Expression Mastery

Anti-Greed

Here's an example where the greedy one is less efficient.

Greedy Version

/a+(a|b)/

aaab

             START             |a a a b
             a                 |a a a b         Yes!
             +                 <a|a a b
              a                <a|a a b         Yes!
              +                <a a|a b
               a               <a a|a b         Yes!
               +               <a a a|b
                |              <a a a|b
                 a             <a a a|b         Nope
                 b             <a a a|b         Yes!
                END            <a a a b>        Yes!

We reached END, so the match succeeds; it found the aaab part of aaab