Regular Expressions 101 Trivia Quiz

Answer: ABBA

The "?" quantifier means a match of zero or one occurrences of the character preceding it. The regular expression "AB?B?C?A" is evaluated as follows: an "A" followed by zero or one "B"s followed by zero or one "B"s followed by zero or one "C"s followed by an "A". Thus, "ABBA" is a match.

Answer: ACE

The "+" quantifier means a match of zero or more occurrences of the character preceding it. The regular expression "AB?C+E" is evaluated as follows: an "A" followed by zero or more "B"s followed by one or more "C"s followed by an "E". Thus, "ACE" is a match.

Answer: BBC6

The "*" quantifier means a match of zero or more occurrences of the character preceding it. The "[]" quantifier means an occurrence of a character defined within the brackets. The regular expression "B*C[2-6]" is evaluated as follows: zero or more "B"s followed by a "C" followed by a digit in the range 2-6. Thus, "BBC6" is a match.

Answer: ABDC

The "." quantifier means a single occurrence of the any character. Hence, the regular expression "A..C" is evaluated as follows: an "A" followed by any two characters followed by a "C". Thus, "ABDC" is a match.

Answer: ABODE

Best to interpret the regular expression "^A[BC]OD[EF]$" as we go along. The "^" quantifier means match a line starting with the character following it. So, we are looking for a match starting with an "A". The square brackets mandate a character from the selection within them hence the following letter should be a "B" or a "C". Next should come a hard coded "OD".

The last character of the line, signified by the "$" quantifier, must be an "E" or an "F". The word "ABODE" matches this complex criteria.

Answer: ABC1

The "\d" quantifier means an occurrence of a decimal digit. So the regular expression "ABC\d" is evaluated as follows: an "ABC" followed by a digit to which "ABC1" is a match. An alternative form of this regular expression would be "ABC[0-9]".

Answer: ABCD

The "|" quantifier means an occurrence of any one of the pipe-separated characters. The regular expression "(A|B)(B|C)[^D](C|D)$" is evaluated as follows: an "A" or a "B" followed by a "B" or a "C" followed by a character that's not "D" and ending with a "C" or a "D". From the options, only "ABCD" matches this pattern.

Answer: CAB

The "[]" quantifier means an occurrence of any character defined within the brackets. "[A-C]" refers to any character in the range A-C. "[-AC]" just means a "-" or an "A" or a "C". So, "CAB" is a match.

Answer: DAB

The "[^]" quantifier means an occurrence of any character except the ones defined within the brackets. "[^A-C]" refers to any character except the ones in the range A-C. "[-AC]" just means a "-" or an "A" or a "C". "[A-C]" refers to any character in the range A-C. Thus, "DAB" is a match.

Answer: ABCDE

The "+" quantifier means one or more occurrences of the character preceding it. Hence, the regular expression "A+B+C+D+E+" should be evaluated as an "ABCDE" string with possibly more of each letter adjacent to itself, with the mere "ABCDE" being a minimal match.