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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