# Regular Expression (RE) for starting with 0 and ending with 1

## Regular Expression (RE) for starting with 0 and ending with 1

Let us see the Regular Expression (RE) for starting with 0 and ending with 1 defined over {0,1}.

## Rule

All strings starting with 0 and ending with 1 must be accepted and all other strings must be rejected by our Regular Expression.

# Regular Expression= 0(0+1)* 1

## 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, 0, no more strings}
• 3 strings of length 2 = {10, 00, 11}
• 3 strings of length 3 = {101, 110, 000}
• 3 strings of length 4 = {1001, 0110, 1000}
• 3 strings of length 7 = {01000, 10111, 11000}
• 3 strings of length 10 = {0000000000, 1111111111, 1000011110}
• 3 strings of length 15 = {000000000000000, 111111111111111, 100000001111110}
• 3 strings of length 20 = {10000000000000000000, 01111111111111111110, 10001110000001111111}
• 3 strings of length 25 = {1000000000001111100000001, 0111110000011111111111110, 1000111000111110001111110}
• Many other similar strigs.

## 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 = {no string exist}
• 3 strings of length 2 = {01, no more strings}
• 3 strings of length 3 = {001, 011, no more strings}
• 3 strings of length 4 = {0001, 0111,0011, 0101, no more strings }
• 3 strings of length 7 = {0000001, 0111111, 0000111, many other similar strigs}
• 3 strings of length 10 = {0000000001, 0111111111, 0000011111, many other similar strigs }
• 3 strings of length 15 = {000000000000001, 011111111111111, 000000001111111, many other similar strigs }
• 3 strings of length 20= {00000000000000000001, 01111111111111111111, 00001110000001111111, many other similar strigs }
• 3 strings of length 25 = {0000000000001111100000001, 0111110000011111111111111, 0000111000111110001111111, many other similar strigs }
• Many other similar strigs.

## Regular Expression (RE) for starting with a and ending with b

Let us see the Regular Expression (RE) for starting with a and ending with b defined over {a,b}.

Rule:

All strings starting with a and ending with b must be accepted and all other strings must be rejected by our Regular Expression.

# Regular Expression= a(a+b)* b

## 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 = {b, a, no more strings}
• 3 strings of length 2 = {ba, aa, bb}
• 3 strings of length 3 = {bab, bba, aaa}
• 3 strings of length 4 = {baab, abba, baaa}
• 3 strings of length 7 = {abaaa, babbb, bbaaa}
• 3 strings of length 10 = {aaaaaaaaaa, bbbbbbbbbb, baaaabbbba}
• 3 strings of length 15 = {aaaaaaaaaaaaaaa, bbbbbbbbbbbbbbb, baaaaaaabbbbbba}
• 3 strings of length 20 = {baaaaaaaaaaaaaaaaaaa, abbbbbbbbbbbbbbbbbba, baaabbbaaaaaabbbbbbb}
• 3 strings of length 25 = {baaaaaaaaaaabbbbbaaaaaaab, abbbbbaaaaabbbbbbbbbbbbba, baaabbbaaabbbbbaaabbbbbba}
• Many other similar strigs

## 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 = {no string exist}
• 3 strings of length 2 = {ab, no more strings}
• 3 strings of length 3 = {aab, abb, no more strings}
• 3 strings of length 4 = {aaab, abbb,aabb, abab, no more strings }
• 3 strings of length 7 = {aaaaaab, abbbbbb, aaaabbb, many other similar strigs}
• 3 strings of length 10 = {aaaaaaaaab, abbbbbbbbb, aaaaabbbbb, many other similar strigs }
• 3 strings of length 15 = {aaaaaaaaaaaaaab, abbbbbbbbbbbbbb, aaaaaaaabbbbbbb, many other similar strigs }
• 3 strings of length 20= {aaaaaaaaaaaaaaaaaaab, abbbbbbbbbbbbbbbbbbb, aaaabbbaaaaaabbbbbbb, many other similar strigs }
• 3 strings of length 25 = {aaaaaaaaaaaabbbbbaaaaaaab, abbbbbaaaaabbbbbbbbbbbbbb, aaaabbbaaabbbbbaaabbbbbbb, many other similar strigs }
• Many other similar strigs.

## 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.