## RE for starting with 1 having zero or multiple even 1’s

## , defined over{1}

**Regular Expression = (11)***

## RE for starting with 1 and after starting 1 can have no 1 or multiple even 1’s, defined over{1}

## Rule

All strings starting with 1 and then after first one having zero or multiple even 1’s must be accepted and all other strings must be rejected by our Regular Expression.

**Regular Expression = 1(11)***

## Reject able strings (not part of the language)

These strings are not part of the given language and must be rejected by our Regular Expression.

- 3 strings of length 1 = {No string}
- 3 strings of length 2 = {11}
- 3 strings of length 3= {no string}
- 3 strings of length 4 = {1111}
- 3 strings of length 7 = {no string}
- 3 strings of length 10 = {1111111111}
- 3 strings of length 15 = {no string}
- 3 strings of length 20 = {11111111111111111111}
- 3 strings of length 25 = {no string}
- Many More similar strings.

## Acceptable strings (part of the language)

These strings are part of the given language and must be accepted by our Regular Expression.

- 3 strings of length 1 = {1, no more strings}
- 3 strings of length 2 = {No string}
- 3 strings of length 3= {111, no more strings}
- 3 strings of length 4 = {No Strings}
- 3 strings of length 7 = {1111111, no more strings}
- 3 strings of length 10 = {NO Strings}
- 3 strings of length 15 = {111111111111111, no more strings}
- 3 strings of length 20= {No Strings}
- 3 strings of length 25= {1111111111111111111111111}
- Many More similar strings.

## RE for starting with a having one a and then having zero or multiple even a’s

## Rule

All strings starting with a and then after first one having zero or multiple even a’s must be accepted and all other strings must be rejected by our Regular Expression.

**Regular Expression = a(aa)***

## Reject able strings (not part of the language)

These strings are not part of the given language and must be rejected by our Regular Expression.

- 3 strings of length 1 = {No string}
- 3 strings of length 2 = {aa}
- 3 strings of length 3= {no string}
- 3 strings of length 4 = {aaaa}
- 3 strings of length 7 = {no string}
- 3 strings of length 10 = {aaaaaaaaaa}
- 3 strings of length 15 = {no string}
- 3 strings of length 20 = {aaaaaaaaaaaaaaaaaaaa}
- 3 strings of length 25 = {no string}
- Many More similar strings.

## Acceptable strings (part of the language)

These strings are part of the given language and must be accepted by our Regular Expression.

- 3 strings of length 1 = {a, no more strings}
- 3 strings of length 2 = {No string}
- 3 strings of length 3= {aaa, no more strings}
- 3 strings of length 4 = {No Strings}
- 3 strings of length 7 = {aaaaaaa, no more strings}
- 3 strings of length 10 = {NO Strings}
- 3 strings of length 15 = {aaaaaaaaaaaaaaa, no more strings}
- 3 strings of length 20= {No Strings}
- 3 strings of length 25= {aaaaaaaaaaaaaaaaaaaaaaaaa}
- Many More similar strings.

## More Examples of Regular Expression

- Regular Expression for no 0 or many triples of 0’s and many 1 in the strings.
- RegExp for strings of one or many 11 or no 11.
- A regular expression for ending with abb
- A regular expression for all strings having 010 or 101.
- Regular expression for Even Length Strings defined over {a,b}
- Regular Expression for strings having at least one double 0 or double 1.
- Regular Expression of starting with 0 and having multiple even 1’s or no 1.
- Regular Expression for an odd number of 0’s or an odd number of 1’s in the strings.
- Regular Expression for having strings of multiple double 1’s or null.
- Regular Expression (RE) for starting with 0 and ending with 1.
- RE for ending with b and having zero or multiple sets of aa and bb.
- A regular expression of the second last symbol is 1.
- RE for starting with 1 having zero or multiple even 1’s.
- Regular Expression for multiple a’s and multiple b’s.
- RE for exactly single 1 many 0’s |exactly single a many b.
- A regular expression for strings starting with aa and ending with ba.
- A regular expression for the language of all consecutive even length a’s.
- A regular expression for the language of all odd-length strings
- A regular expression for the language of all even length strings but ends with aa.
- A regular expression for the language of an odd number of 1s.
- A regular expression for the language of even length strings starting with a and ending with b in theory of automata.
- A regular expression for the language of all even length strings but starts with a.
- A Regular Expression for the Language of all strings with an even number of 0’s or even number of 1’s.
- A regular expression for the language of all those strings end with abb.
- A regular expression for string having must 010 or 101.
- Regular expression of strings begin with 110

Regular expression of strings begin and end with 110

Regular expression of strings containing exactly three consecutive 1’s. - A Regular Expression of all strings divisible by 4.
- A Regular Expression Strings that does not contain substring 110.

## Tutorial: Regular Expression

A detailed tutorial of the regular expression is here in the link of regular expression tutorial. This page contains the practice questions of regular expressions with solutions.

**Tutorial covering the topics**

- Give a regular expression.
- Describe the strings of the regular expression.
- write a regular expression.
- create all strings from regular expression.
- Generate all strings from regular expression.
- Extract all strings from regular expression.
- Find all strings from regular expression.
- Examples of regular expression.