1. If doable, find a regular expression for the following languages over alphabet {a, b}. i. Strings with an odd number of a ii. Both the number of a's and the number of b's are even iii. No string contains the substring aa iv. {a2n|ne N} U {b2n+1 | n € N} while N= {0,1,2,3,...}

2- Write a regular expression for each of the following languages over {a,b}: • String of a's and b's that begin with a and end with b. • Strings that have at least two a's. • Strings that have an even number of a's. • Strings that do not have two a's in a row. • Strings that do not end with the substring ab.

1. For each of the following regular expressions find a language (i.e., a set of strings over A = {a,b.c} that can be represented/described by that expression. a. a'bc + bc* b. b'aaac а. b.

NLP Q#2: Write regular expressions for the following languages. By "word", we mean an alphabetic string separated from other words by whitespace, any relevant punctuation, line breaks, and so forth. 1. the set of all strings with two consecutive repeated words (e.g., "Humbert Humbert" and "the the" but not "the bug" or "the big bug"); 2. all strings that start at the beginning of the line with an integer and that end at the end of the line with a word; 3. all strings that have both the word grotto and the word raven in them (but not, e.g., words like grottos that merely contain the word grotto); 4. Demonstrate a pattern to check if the email address is valid. 5. Demonstrate a pattern to verify the validity of a phone number, and check if it belongs to the Pakistani Mobile Network. 6. Demonstrate a RE to remove symbols and non-alphanumeric characters from the string paragraph. 7. Demonstrate a RE to remove URLs and HTML tags from the text string.

ans asap and completely

language L=<E,n> E is an enumerator, n is a number. <E,n> means language enumerated by E with length n. Is L recognizable? Is L decidable?

Write Context Free Grammers for: All strings having even a’s and odd b’s All strings that start and end with different letters anbn anbman

Let E= {a, b}. Given regular expressions r = a*b*, r' = ba(ab)* + ab*ba* and r" = (a + b)aa(a + b)*, find L(r), L(r'), and L(r"), the languages defined by r, r', r", respectively.

Assignment Content Given two strings s and t, determine if they are isomorphic. Two strings s and t are isomorphic if the characters in s can be replaced to get t. All occurrences of a character must be replaced with another character while preserving the order of characters. No two characters may map to the same character, but a character may map to itself. Example 1: Input: s="egg", t = "add" Output: true Example 2: Input: s="foo", t = "bar" Output: false Example 3: Input: s= "paper", t = "title" Output: true

For each one of the following languages over alphabet {a, b}, write an equivalent regular expression. (a) All strings made out of zero or more b's: (b) All strings that do not start with bb. (c) All strings that end with aaa or bb (d) All strings that start and end with the same alphabet letter.