Day 4 High-Entropy Passphrases

Let’s get down to business with Day 4.

4.1 Part I

A new system policy has been put in place that requires all accounts to use a passphrase instead of simply a password. A passphrase consists of a series of words (lowercase letters) separated by spaces.

To ensure security, a valid passphrase must contain no duplicate words.

For example:

aa bb cc dd ee is valid.
aa bb cc dd aa is not valid - the word aa appears more than once.
aa bb cc dd aaa is valid - aa and aaa count as different words.

The system's full passphrase list is available as your puzzle input. How many passphrases are valid?

Here’s what the beginning of my puzzle input looked like:

We are interested in determining if each passphrase is valid, so let’s start with a function:

Let’s test it out to make sure it works the way we think it does:

## [1] TRUE
## [1] FALSE

With our function, we just need to reformat our puzzle input a bit and pipe everything through.

## # A tibble: 1 x 1
##     sum
##   <int>
## 1    16

Easy peasy!

4.2 Part II

For added security, yet another system policy has been put in place. Now, a valid
passphrase must contain no two words that are anagrams of each other - that is, a
passphrase is invalid if any word's letters can be rearranged to form any other word
in the passphrase.

For example:

abcde fghij is a valid passphrase.
abcde xyz ecdab is not valid - the letters from the third word can be rearranged to form the first word.
a ab abc abd abf abj is a valid passphrase, because all letters need to be used when forming another word.
iiii oiii ooii oooi oooo is valid.
oiii ioii iioi iiio is not valid - any of these words can be rearranged to form any other word.

Under this new system policy, how many passphrases are valid?

To deal with anagrams, let’s write another function to rearrange all words alphabetically, and then revise validate_passphrase to account for anagrams. We’ll call this new function, validate_anagrams.

Now that we have our new function, we can stick it into the same pipe as before to get our answer! :star:

## # A tibble: 1 x 1
##     sum
##   <int>
## 1     9