Question $3-$ Text Processing $-10$ points

$(2$ pts$)[$Regex$]$ A Java variable name must start with an alpha$-$character $\{A-Z,a-Z\}$ or underscore $-$ and cannot start with a digit and has a maximum of $32$ characters chosen from alpha$-$numeric characters $($includes A$-$Z a$-$Z $0-9)$ or underscopre $-$ Write a regular expression to describe any Java variable name.

Consider the following $4$ sentences.

S$1=$ "Sam Sam I am Sam"

$S2=$ "I like Sam like Fish Chips"

$53=$ "Sam Sam Fish Chips"

$54=$ "Fish Chips like Sam Chips"

$($a$)(4$ pts$)$ Create the term$-$frequency matrix TF where rows are sentences and columns are words.

Sam I am Fish Chips like

S$1$

S$2$

S$3$

$S4$

$($b$)(4$ pts$)$ Using L$1$ or Manhattan distance between two sentence vectors in the TF matrix, create the $4x4$ distance matrix. Using the matrix of distances, group Sentences into two clusters where sentences are "similar". Use any tie breaking rule and clearly describe your algorithm.