$1Interesting challenges for regular expression newbie like me~

TBC...

Classic

Warmup

foo

Anchors

k$

It never ends

u\b

should work on PCRE: u\Z

Ranges

^[a-f]*$

Backrefs

I think this is useful.

noooooooooo

We need back references.

(...).*\1

Abba

This is hard for me ...

^(?!.*(\w)(\w)\2\1)

How does these guys use 14 character but not 19?

ok, ^(?!.*(.)(.)\2\1) for 17

^(?!.*(.)\1)|ef for 15

^(?!(.)+\1)|ef for 14,,, WTF

A man, a plan

It's Palindrome.

But it seems doesn't support PCRE,,,

^(.)(.).*\2\1$ for 14. Not perfect answer.

(.)[^p].*\1$ for 13, but not fun.

Prime

WTF???

Wow, really interesting!!!

^(?!(..+)\1+$)

Four

(\w).\1.\1.\1 for 13. How to achieve 11?

Oh I got it:(.)(.\1){3}

Order

^[^o].{4,5}$ for 12

^[^o]?.{5}$ for 11 or ^.{5}[^e]?$

Triples

Powers

^(?!(.(..)+)\1*$)`