85 lines
3.5 KiB
Markdown
85 lines
3.5 KiB
Markdown
## \-\-- Day 8: Matchsticks \-\--
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Space on the sleigh is limited this year, and so Santa will be bringing
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his list as a digital copy. He needs to know how much space it will take
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up when stored.
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It is common in many programming languages to provide a way to
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escape
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special characters in strings. For example,
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[C](https://en.wikipedia.org/wiki/Escape_sequences_in_C),
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[JavaScript](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String),
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[Perl](http://perldoc.perl.org/perlop.html#Quote-and-Quote-like-Operators),
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[Python](https://docs.python.org/2.0/ref/strings.html), and even
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[PHP](http://php.net/manual/en/language.types.string.php#language.types.string.syntax.double)
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handle special characters in very similar ways.
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However, it is important to realize the difference between the number of
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characters *in the code representation of the string literal* and the
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number of characters *in the in-memory string itself*.
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For example:
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- `""` is `2` characters of code (the two double quotes), but the
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string contains zero characters.
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- `"abc"` is `5` characters of code, but `3` characters in the string
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data.
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- `"aaa\"aaa"` is `10` characters of code, but the string itself
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contains six \"a\" characters and a single, escaped quote character,
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for a total of `7` characters in the string data.
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- `"\x27"` is `6` characters of code, but the string itself contains
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just one - an apostrophe (`'`), escaped using hexadecimal notation.
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Santa\'s list is a file that contains many double-quoted string
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literals, one on each line. The only escape sequences used are `\\`
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(which represents a single backslash), `\"` (which represents a lone
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double-quote character), and `\x` plus two hexadecimal characters (which
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represents a single character with that ASCII code).
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Disregarding the whitespace in the file, what is *the number of
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characters of code for string literals* minus *the number of characters
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in memory for the values of the strings* in total for the entire file?
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For example, given the four strings above, the total number of
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characters of string code (`2 + 5 + 10 + 6 = 23`) minus the total number
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of characters in memory for string values (`0 + 3 + 7 + 1 = 11`) is
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`23 - 11 = 12`.
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Your puzzle answer was `1342`.
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## \-\-- Part Two \-\-- {#part2}
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Now, let\'s go the other way. In addition to finding the number of
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characters of code, you should now *encode each code representation as a
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new string* and find the number of characters of the new encoded
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representation, including the surrounding double quotes.
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For example:
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- `""` encodes to `"\"\""`, an increase from `2` characters to `6`.
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- `"abc"` encodes to `"\"abc\""`, an increase from `5` characters to
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`9`.
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- `"aaa\"aaa"` encodes to `"\"aaa\\\"aaa\""`, an increase from `10`
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characters to `16`.
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- `"\x27"` encodes to `"\"\\x27\""`, an increase from `6` characters
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to `11`.
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Your task is to find *the total number of characters to represent the
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newly encoded strings* minus *the number of characters of code in each
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original string literal*. For example, for the strings above, the total
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encoded length (`6 + 9 + 16 + 11 = 42`) minus the characters in the
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original code representation (`23`, just like in the first part of this
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puzzle) is `42 - 23 = 19`.
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Your puzzle answer was `2074`.
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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](/2015) 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](8/input).
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