# Regular Expression of starting with 0 and having multiple even 1’s or no 1

## Regular Expression of starting with 0 and having multiple even 1’s or no 1

Regular Expression = 0 0*(10*10*)*

## Regular Expression of starting with 0 and having multiple consecutive 11’s or no 1 in the string. 0 must be only one time in the regular expression.

Let us see the Regular Expression of all those strings starting with 0 and having multiple even 1’s or no 1, having only one 0, defined over {0,1}

Regular Expression = 0(11)*

## Rule

All those strings starting with 0 and having multiple even 1’s or no 1 must be accepted and all other strings must be rejected by our Regular Expression.

## Rejectable 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, no more string}
• 3 strings of length 2 = {11, 00, no more string}
• 3 strings of length 3= {001,000,100}
• 3 strings of length 4 = {0010, 0001, 0100}
• 3 strings of length 7 = {0111000, 0111110, 0011100}
• 3 strings of length 10 = {0000011111, 0011100001}
• 3 strings of length 15 = {000000000011111, 000001111100000, 000111111111000}
• 3 strings of length 20 = {00000000000111111111, 00000011111110000111, 00001111111000000000}
• 3 strings of length 25 = {0000000000000011111111111, 0000000000111111111111100, 0000000000111111111000111}
• Many other 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 = {0, no string}
• 3 strings of length 2 = {no string}
• 3 strings of length 3= {011, no more string}
• 3 strings of length 4 = {no string}
• 3 strings of length 7 = {0111111, no more string}
• 3 strings of length 10 = {no string}
• 3 strings of length 15 = {011111111111111, no more string}
• 3 strings of length 20= {no string}
• 3 strings of length 25= {0111111111111111111111111, no more string}
• Many other strings.

## Regular Expression of all those strings starting with a and having multiple even b’s or no b

Let us see the Regular Expression of all those strings starting with a and having multiple even b’s or no b defined over {a,b}

# Regular Expression = a(bb)*

## Rule

All those strings starting with a and having multiple even b’s or no b must be accepted and all other strings must be rejected by our Regular Expression.

## Rejectable 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 = {b, no more string}
• 3 strings of length 2 = {bb, aa, no more string}
• 3 strings of length 3= {aab,aaa,baa}
• 3 strings of length 4 = {aaba, aaab, abaa}
• 3 strings of length 7 = {abbbaaa, abbbbba, aabbbaa}
• 3 strings of length 10 = {aaaaabbbbb, aabbbaaaab}
• 3 strings of length 15 = {aaaaaaaaaabbbbb, aaaaabbbbbaaaaa, aaabbbbbbbbbaaa}
• 3 strings of length 20 = {aaaaaaaaaaabbbbbbbbb, aaaaaabbbbbbbaaaabbb, aaaabbbbbbbaaaaaaaaa}
• 3 strings of length 25 = {aaaaaaaaaaaaaabbbbbbbbbbb, aaaaaaaaaabbbbbbbbbbbbbaa, aaaaaaaaaabbbbbbbbbaaabbb}
• Many other 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 string}
• 3 strings of length 2 = {no string}
• 3 strings of length 3= {abb, no more string}
• 3 strings of length 4 = {no string}
• 3 strings of length 7 = {abbbbbb, no more string}
• 3 strings of length 10 = {no string}
• 3 strings of length 15 = {abbbbbbbbbbbbbb, no more string}
• 3 strings of length 20= {no string}
• 3 strings of length 25= {abbbbbbbbbbbbbbbbbbbbbbbb, no more string}
• Many other strings.

Regular Expression of starting with 0 and having multiple even 1’s or no 1

## 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.