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89 lines
3.3 KiB
Markdown
89 lines
3.3 KiB
Markdown
3 years ago
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https://adventofcode.com/2021/day/10
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## \--- Day 10: Syntax Scoring ---
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You ask the submarine to determine the best route out of the deep-sea cave,
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but it only replies:
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[code]
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Syntax error in navigation subsystem on line: all of them
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[/code]
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_All of them?!_ The damage is worse than you thought. You bring up a copy of
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the navigation subsystem (your puzzle input).
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The navigation subsystem syntax is made of several lines containing _chunks_.
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There are one or more chunks on each line, and chunks contain zero or more
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other chunks. Adjacent chunks are not separated by any delimiter; if one chunk
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stops, the next chunk (if any) can immediately start. Every chunk must _open_
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and _close_ with one of four legal pairs of matching characters:
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* If a chunk opens with `(`, it must close with `)`.
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* If a chunk opens with `[`, it must close with `]`.
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* If a chunk opens with `{`, it must close with `}`.
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* If a chunk opens with `<`, it must close with `>`.
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So, `()` is a legal chunk that contains no other chunks, as is `[]`. More
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complex but valid chunks include `([])`, `{()()()}`, `<([{}])>`,
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`[<>({}){}[([])<>]]`, and even `(((((((((())))))))))`.
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Some lines are _incomplete_ , but others are _corrupted_. Find and discard the
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corrupted lines first.
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A corrupted line is one where a chunk _closes with the wrong character_ \-
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that is, where the characters it opens and closes with do not form one of the
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four legal pairs listed above.
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Examples of corrupted chunks include `(]`, `{()()()>`, `(((()))}`, and
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`<([]){()}[{}])`. Such a chunk can appear anywhere within a line, and its
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presence causes the whole line to be considered corrupted.
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For example, consider the following navigation subsystem:
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[code]
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[({(<(())[]>[[{[]{<()<>>
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[(()[<>])]({[<{<<[]>>(
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{([(<{}[<>[]}>{[]{[(<()>
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(((({<>}<{<{<>}{[]{[]{}
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[[<[([]))<([[{}[[()]]]
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[{[{({}]{}}([{[{{{}}([]
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{<[[]]>}<{[{[{[]{()[[[]
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[<(<(<(<{}))><([]([]()
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<{([([[(<>()){}]>(<<{{
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<{([{{}}[<[[[<>{}]]]>[]]
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[/code]
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Some of the lines aren't corrupted, just incomplete; you can ignore these
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lines for now. The remaining five lines are corrupted:
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* `{([(<{}[<>[]}>{[]{[(<()>` \- Expected `]`, but found `}` instead.
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* `[[<[([]))<([[{}[[()]]]` \- Expected `]`, but found `)` instead.
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* `[{[{({}]{}}([{[{{{}}([]` \- Expected `)`, but found `]` instead.
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* `[<(<(<(<{}))><([]([]()` \- Expected `>`, but found `)` instead.
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* `<{([([[(<>()){}]>(<<{{` \- Expected `]`, but found `>` instead.
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Stop at the first incorrect closing character on each corrupted line.
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Did you know that syntax checkers actually have contests to see who can get
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the high score for syntax errors in a file? It's true! To calculate the syntax
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error score for a line, take the _first illegal character_ on the line and
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look it up in the following table:
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* `)`: `3` points.
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* `]`: `57` points.
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* `}`: `1197` points.
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* `>`: `25137` points.
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In the above example, an illegal `)` was found twice (`2*3 = _6_` points), an
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illegal `]` was found once (` _57_` points), an illegal `}` was found once (`
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_1197_` points), and an illegal `>` was found once (` _25137_` points). So,
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the total syntax error score for this file is `6+57+1197+25137 = _26397_`
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points!
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Find the first illegal character in each corrupted line of the navigation
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subsystem. _What is the total syntax error score for those errors?_
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