# Regular Expression: (11) *

## Rule:

All strings having strings of multiple double 1’s or null must be accepted and all other strings must be rejected by our Regular Expression.

## Rejected 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 = {1}
• 3 strings of length 2 = {no string exist}
• 3 strings of length 3 = {111, no more strings}
• 3 strings of length 5 = {11111, no more strings}
• 3 strings of length 7 = {1111111, no more strings}}
• 3 strings of length 9 = {111111111, no more strings}
• 3 strings of length 15 = {111111111111111, no more strings}
• 3 strings of length 20 = {no string exist}
• 3 strings of length 25 = {1111111111111111111111111, no more strings}
• Many more strings.

## Accepted 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 = {null}
• 3 strings of length 2 = {11}
• 3 strings of length 3 = {no string exists}
• 3 strings of length 4 = {1111, no more strings}
• 3 strings of length 7 = {no string exists}
• 3 strings of length 10 = {1111111111, no more strings}
• 3 strings of length 15 = {no string exists}
• 3 strings of length 20= {11111111111111111111, no more strings}
• 3 strings of length 25 = {no string exists}
• Many more strings.

# Regular Expression: (aa) *

## Rule:

All strings having strings of multiple double a’s or null must be accepted and all other strings must be rejected by our Regular Expression.

## Rejected 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 = {a}
• 3 strings of length 2 = {no string exist}
• 3 strings of length 3 = {aaa, no more strings}
• 3 strings of length 5 = {aaaaa, no more strings}
• 3 strings of length 7 = {aaaaaaa, no more strings}}
• 3 strings of length 9 = {aaaaaaaaa, no more strings}
• 3 strings of length 15 = {aaaaaaaaaaaaaaa, no more strings}
• 3 strings of length 20 = {no string exist}
• 3 strings of length 25 = {aaaaaaaaaaaaaaaaaaaaaaaaa, no more strings}
• Many more strings.

## Accepted 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= {null}
• 3 strings of length 2 = {aa}
• 3 strings of length 3 = {no string exists}
• 3 strings of length 4 = {aaaa, no more strings}
• 3 strings of length 7 = {no string exists}
• 3 strings of length 10 = {aaaaaaaaaa, no more strings}
• 3 strings of length 15 = {no string exists}
• 3 strings of length 20= {aaaaaaaaaaaaaaaaaaaa, no more strings}
• 3 strings of length 25 = {no string exists}
• Many more strings.

Regular Expression for having strings of multiple double 1s or null

## 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.