Code is in Rust.

Will be checked. Can only use regex crate and standard rust library. No unsafe.

pub fn read$\_$prices$($filename: &str$)->$ Option$>$

Given a txt file, parse and return the items sold by a vending machine, along with their prices. Alternatively, return None if the file has an invalid

format.

Each line of the the file must either be a price listing or a comment.

Price listings consist of the following in the order shown:

an item name $($starts with an uppercase $($ A $-$ Z $)$ or lowercase $($ a$-$z $)$ letter, followed by any number of such letters or space

characters$)$

a semi$-$colon ;

a price in cents $($any integer$)$

c or cents.

Each of these can be separated by an arbitrary number of spaces. That includes $0$ spaces. These should not be included in your

hashmap. $($You may assume no spaces at the very beginning of a line.$)$

Comment lines start with ; and can contain any characters after that. They should be ignored.

Validity:

An item's price must be between $1$ and $50$ cents $($inclusive$).$ An item must appear at most once in the file, duplicates are not allowed. If any of

these rules are violated, or if any line has an invalid format, you must return None $.$

You can use the regex crate to implement the rules above. Example Files

$```$

;file$1.$txt

; sweet

ice cream; $10$ cents

; savory

sandwich;$49$c

hot dog ; $49$ c

$```$

;file$2.$txt

;icecream;$10$cents

ice cream; $10$ cents

; lines below are invalid

goldfish; $100$c

sandwich; $49$c cents

;file$3.$txt

cat ; cats are not snacks

chips ; $20$c

;meow.txt $($this is a valid file$)$

here kittykitty; $1$c