字符和數字至少出現一次

Question

我希望下面的正則表達式可以匹配字符串「a34cvDrerevbf98f04389」，

\b[0-9a-zA-Z]{21}\b 

然而，我發現正則表達式也可以匹配下列字符串，

000001111122222333334 
    #The string doesn't include a character. 

    AbstractAlgebraTheory 
    #The string doesn't include a digit. 

它是否有辦法確保字符和數字在字符串中至少出現一次？

Answer 1

使用向前看。

\b(?=.*\d)(?=.*[a-zA-Z])[0-9a-zA-Z]{21}\b 

如有必要添加錨點。

^(?=.*\d)(?=.*[a-zA-Z])[0-9a-zA-Z]{21}$