Warm Up
Answer： foo Point(3)
Anchors
Answer: k$ Point(2)
It never ends $ not allowed
Answer: fu\b Point(4) 或者 u\b
Ranges
Answer:[a-f][a-f][a-f][a-f] Point(20)
Backrefs
Answer: (...).*\1 Point(9)
Abba
Answer: ^(?!.*(.)(.)\2\1) Point(17)
A man, a plan
Answer: ^(.)(.).*\2\1$
Four
Answer: ([aioe]).\1.\1.\1
Order
Answer: ^[a-m][c-o][c-t][e-t][i-z][n-z]?$
Prime
Answer: ^(?!(..+)\1+$)
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