A Regular Expression of all strings divisible by 4 defined over {a,b}.

**Regular Expression: {(1+0) (1+0) (1+0) (1+0)}***

**Accepted Strings (part of the language)**

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

- The strings of length 01 = {no string exist}
- The strings of length 02 = {no string exist}
- The strings of length 03 = {no string exist}
- The strings of length 04= {1111, 1010, 1001,…. and many more similar strings.}
- The strings of length 07 = {no string exist}
- The strings of length 08 = {10101010, 11001100, 11000011,…. and many more similar strings.}
- The strings of length 10 = {no string exist}
- The strings of length 12 = {111111000000, 111000111000, 101010101010,…. and many more similar strings.}
- The strings of length 20 = {11111000001111100000, 10101010101010101010, 11100011100101001101,…. and many more similar strings.}
- The strings of length 25 = {no string exist}
- And many more similar strings.

**Rejected Strings (not part of the language)**

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

- The strings of length 01 = {0, 1,…. and many more similar strings.}
- The strings of length 02 = {11, 10, 00,…. and many more similar strings.}
- The strings of length 03 = {111, 101, 000,…. and many more similar strings.}
- The strings of length 04 = {no string exist}
- The strings of length 07 = {1100110, 1111111, 0000111,…. and many more similar strings.}
- The strings of length 10 = {1100110011, 1111100000, 1010101010,…. and many more similar strings.}
- The strings of length 15 = {101010101010101, 111110001111000, 111111100000000,…. and many more similar strings.}
- The strings of length 20 = {no string exist}
- The strings of length 25 = {no string exist}
- And many more similar strings.

**Regular Expression of set of all strings divisible by 4**

**Regular Expression: {(b+a) (b+a) (b+a) (b+a)}***

**Accepted Strings (part of the language)**

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

- The strings of length 1 = {no string exist}
- The strings of length 2 = {no string exist}
- The strings of length 3 = {no string exist}
- The strings of length 4= {bbbb, baba, baab,…. and many more similar strings.}
- The strings of length 7 = {no string exist}
- The strings of length 8 = {babababa, bbaabbaa, bbaaaabb,…. and many more similar strings.}
- The strings of length 10 = {no string exist}
- The strings of length 12 = {bbbbbbaaaaaa, bbbaaabbbaaa, babababababa,…. and many more similar strings.}
- The strings of length 20 = {bbbbbaaaaabbbbbaaaaa, babababababababababa, bbbaaabbbaababaabbab,…. and many more similar strings.}
- The strings of length 25 = {no string exist}
- and many more similar strings.

**Rejected Strings (not part of the language)**

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

- The strings of length 1 = {a, b,…. and many more similar strings.}
- The strings of length 2 = {bb, ba, aa, ab}
- The strings of length 3 = {bbb, bab, aaa,…. and many more similar strings.}
- The strings of length 4 = {no string exist}
- The strings of length 7 = {bbaabba, bbbbbbb, aaaabbb,…. and many more similar strings.}
- The strings of length 10 = {bbaabbaabb, bbbbbaaaaa, bababababa,…. and many more similar strings.}
- The strings of length 15 = {bababababababab, bbbbbaaabbbbaaa, bbbbbbbaaaaaaaa,…. and many more similar strings.}
- The strings of length 20 = {no string exist}
- The strings of length 25 = {no string exist}

## 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.

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