Regex to match string not ending with pattern

Question

I try to find a regex that matches the string only if the string does not end with at least three \'0\' or more. Intuitively, I tried:

.*[^0]{3,}$
         


        

Answer 1

This is one of those things that RegExes aren't that great at, because the string isn't very regular (whatever that means). The only way I could come up with was to give it every possibility.

.*[^0]..$|.*.[^0].$|.*..[^0]$

which simplifies to

.*([^0]|[^0].|[^0]..)$

That's fine if you only want strings not ending in three 0s, but strings not ending in ten 0s would be long. But thankfully, this string is a bit more regular than some of these sorts of combinations, and you can simplify it further.

.*[^0].{0,2}$