Question

Describe in plain english what the following regular expressions match:

ab+c

[A-Z][0-9]{6}

\d+ ([A-Z][a-z]+)+\n([A-Z][a-z]+)+,[A-Z]{2} \d{5}\

Write a finite state machine for each of the previous regexs.

Answer 1

The first Regular expression:

[A-Z][0-9]{6} -> It matches a string whose first character is a capital letter from A to Z , followed by 6 digits.

eg. A123456

The finite state machine (NFA) is given below:

The second regular expression.

\d+([A-Z][a-z]+)+\n([A-Z][a-z]+)+,[A-Z]{2} \d{5}\ -> It matches a string starting with atleast one digit, then it has a group one or more times, which contains one capital letter followed by one or more small letters. The string then must have a newline symbol . Then it has another group with properties exactly same as previous group. A comma is there after that. Then there are two capital letter, followed by 5 digits .

The finite state machine (NFA) is given below: