Regular expression over ∑={a,b,c} that represent all string of length

=> **(a+b+c)(a+b+c)(a+b+c)**

String having zero or more

=> **a***

String having one or more

=> **a+**

All binary string.

=>**(0+1)***

0 or more occurrence of either a or b or both

=> **(a+b)***

1 or more occurrence of either a or b or both

=> **(a+b) ^{+}**

Binary number end with 0

=>**(0+1)*0**

Binary number end with 1

=>**(0+1)*1**

Binary starts and end with 1.

=>** 1(0+1)*1**

String starts and ends with same

=> **0(0+1)*0 or 1(0+1)*1 or a(a+b)*a or b(a+b)*b**

All string of a and b starting with a

=>** a(a/b)***

String of 0 and 1 end with 00

=>** (0+1)*00**

String end with abb

=>** (a+b)*abb**

String start with 1 and end with 0

=>** 1(0+1)*0**

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All binary string with at least 3 characters and 3rd character should be 0

=>**(0+1)(0+1)0(0+1)***

Language which consist of exactly two b’s over the set ∑={a,b}

=>**a*ba*ba***

∑={a,b} such that 3rd character from right end of the string is always a

=> **(a+b)*a(a+b)(a+b)**

Any number of a followed by any number of b followed by any number of c.

=>** a*b*c***

binary string should contain at least 3 one

=>** (0+1)*1(0+1)*1(0+1)*1(0+1)***

String should contain exactly Two 1’s

=> **0*10*10***

Length should be at least be 1 and at most 3

=> **(0+1) + (0+1) (0+1) + (0+1) (0+1) (0+1)**

binary string having number of zero should be multiple of 3

=>** (1*01*01*01*)*+1***

[wp_ad_camp_1]

∑={a,b,c} where a are multiple of 3.

=> **((b+c)*a (b+c)*a (b+c)*a (b+c)*)***

binary string having Even number of 0.

=> **(1*01*01*)***

binary string having Odd no. of 1.

=> **0*(10*10*)*10***

String should have odd length

=>** (0+1)((0+1)(0+1))***

String should have even length

=>** ((0+1)(0+1))***

String start with 0 and has odd length

=>** 0((0+1)(0+1))***

String start with 1 and has even length

=> ** 1(0+1)((0+1)(0+1))***

Binary number having Even number of 1

=> ** (0*10*10*)***

String of length 6 or less

=> **(0+1+^) ^{6}**

String ending with 1 and not contain 00

=> **(1+01) ^{+}**

All string begins or ends with 00 or 11

=>** (00+11)(0+1)*+(0+1)*(00+11)**

All string not contains the sub-string 00

=>** (1+01)* (^+0)**

Language of all string containing both 11 and 00 as substring

=> **((0+1)*00(0+1)*11(0+1)*)+ ((0+1)*11(0+1)*00(0+1)*)**

Language of C identifier.

**=> (_+L)(_+L+D)***