54 lines
1.8 KiB
Markdown
54 lines
1.8 KiB
Markdown
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## \-\-- Day 4: High-Entropy Passphrases \-\--
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A new system policy has been put in place that requires all accounts to
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use a *passphrase* instead of simply a pass*word*. A passphrase consists
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of a series of words (lowercase letters) separated by spaces.
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To ensure security, a valid passphrase must contain no duplicate words.
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For example:
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- `aa bb cc dd ee` is valid.
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- `aa bb cc dd aa` is not valid - the word `aa` appears more than
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once.
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- `aa bb cc dd aaa` is valid - `aa` and `aaa` count as different
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words.
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The system\'s full passphrase list is available as your puzzle input.
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*How many passphrases are valid?*
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Your puzzle answer was `383`.
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## \-\-- Part Two \-\-- {#part2}
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For added security, [yet another system
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policy]{title="Because as everyone knows, the number of rules is proportional to the level of security."}
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has been put in place. Now, a valid passphrase must contain no two words
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that are anagrams of each other - that is, a passphrase is invalid if
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any word\'s letters can be rearranged to form any other word in the
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passphrase.
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For example:
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- `abcde fghij` is a valid passphrase.
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- `abcde xyz ecdab` is not valid - the letters from the third word can
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be rearranged to form the first word.
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- `a ab abc abd abf abj` is a valid passphrase, because *all* letters
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need to be used when forming another word.
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- `iiii oiii ooii oooi oooo` is valid.
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- `oiii ioii iioi iiio` is not valid - any of these words can be
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rearranged to form any other word.
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Under this new system policy, *how many passphrases are valid?*
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Your puzzle answer was `265`.
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Both parts of this puzzle are complete! They provide two gold stars:
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\*\*
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At this point, you should [return to your Advent calendar](/2017) and
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try another puzzle.
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If you still want to see it, you can [get your puzzle
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input](4/input).
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