aoc-2021-rust

Advent of Code 2021 Solutions in Rust
git clone https://git.sinitax.com/sinitax/aoc-2021-rust
Log | Files | Refs | README | sfeed.txt

part2 (2577B)

      1--- Part Two ---
      2
      3Now, discard the corrupted lines.  The remaining lines are incomplete.
      4
      5Incomplete lines don't have any incorrect characters - instead, they're missing some closing
      6characters at the end of the line. To repair the navigation subsystem, you just need to figure out
      7the sequence of closing characters that complete all open chunks in the line.
      8
      9You can only use closing characters (), ], }, or >), and you must add them in the correct order so
     10that only legal pairs are formed and all chunks end up closed.
     11
     12In the example above, there are five incomplete lines:
     13
     14
     15 - [({(<(())[]>[[{[]{<()<>> - Complete by adding }}]])})].
     16
     17 - [(()[<>])]({[<{<<[]>>( - Complete by adding )}>]}).
     18
     19 - (((({<>}<{<{<>}{[]{[]{} - Complete by adding }}>}>)))).
     20
     21 - {<[[]]>}<{[{[{[]{()[[[] - Complete by adding ]]}}]}]}>.
     22
     23 - <{([{{}}[<[[[<>{}]]]>[]] - Complete by adding ])}>.
     24
     25
     26Did you know that autocomplete tools also have contests? It's true! The score is determined by
     27considering the completion string character-by-character. Start with a total score of 0. Then, for
     28each character, multiply the total score by 5 and then increase the total score by the point value
     29given for the character in the following table:
     30
     31
     32 - ): 1 point.
     33
     34 - ]: 2 points.
     35
     36 - }: 3 points.
     37
     38 - >: 4 points.
     39
     40
     41So, the last completion string above - ])}> - would be scored as follows:
     42
     43
     44 - Start with a total score of 0.
     45
     46 - Multiply the total score by 5 to get 0, then add the value of ] (2) to get a new total score of
     472.
     48
     49 - Multiply the total score by 5 to get 10, then add the value of ) (1) to get a new total score of
     5011.
     51
     52 - Multiply the total score by 5 to get 55, then add the value of } (3) to get a new total score of
     5358.
     54
     55 - Multiply the total score by 5 to get 290, then add the value of > (4) to get a new total score of
     56294.
     57
     58
     59The five lines' completion strings have total scores as follows:
     60
     61
     62 - }}]])})] - 288957 total points.
     63
     64 - )}>]}) - 5566 total points.
     65
     66 - }}>}>)))) - 1480781 total points.
     67
     68 - ]]}}]}]}> - 995444 total points.
     69
     70 - ])}> - 294 total points.
     71
     72
     73Autocomplete tools are an odd bunch: the winner is found by sorting all of the scores and then
     74taking the middle score. (There will always be an odd number of scores to consider.) In this
     75example, the middle score is 288957 because there are the same number of scores smaller and larger
     76than it.
     77
     78Find the completion string for each incomplete line, score the completion strings, and sort the
     79scores. What is the middle score?
     80
     81