Day 8: Matchsticks

advent-of-code.org

@@ -3720,3 +3720,391 @@ signal is ultimately provided to wire =a=?
 #+RESULTS[61e8544d7d4f32d111e9a666de842ecc4248e390]:
 : 40149
 
+* Day 8: Matchsticks
+Space on the sleigh is limited this year, and so Santa will be
+bringing his list as a digital copy. He needs to know how much space
+it will take up when stored.
+
+It is common in many programming languages to provide a way to escape
+special characters in strings. For example, C, JavaScript, Perl,
+Python, and even PHP handle special characters in very similar ways.
+
+However, it is important to realize the difference between the number
+of characters *in the code representation of the string literal* and
+the number of characters *in the in-memory string itself*.
+
+For example:
+
+- =""= is =2= characters of code (the two double quotes), but the
+  string contains zero characters.
+- ="abc"= is =5= characters of code, but 3 characters in the string
+  data.
+- ="aaa\"aaa"= is =10= characters of code, but the string itself
+  contains six ="a"= characters and a single, escaped quote character,
+  for a total of =7= characters in the string data.
+- ="\x27"= is =6= characters of code, but the string itself contains
+  just one - an apostrophe (='=), escaped using hexadecimal notation.
+
+Santa's list is a file that contains many double-quoted string
+literals, one on each line. The only escape sequences used are =\\=
+(which represents a single backslash), =\"= (which represents a lone
+double-quote character), and =\x= plus two hexadecimal characters
+(which represents a single character with that ASCII code).
+
+Disregarding the whitespace in the file, what is *the number of
+characters of code for string literals* minus *the number of
+characters in memory for the values of the strings* in total for the
+entire file?
+
+For example, given the four strings above, the total number of
+characters of string code =(2 + 5 + 10 + 6 = 23)= minus the total
+number of characters in memory for string values =(0 + 3 + 7 + 1 =
+11)= is =23 - 11 = 12=.
+
+----------------------------------------------------------------------
+
+:HIDDEN:
+#+name: 8-input
+#+BEGIN_EXAMPLE
+  "qxfcsmh"
+  "ffsfyxbyuhqkpwatkjgudo"
+  "byc\x9dyxuafof\\\xa6uf\\axfozomj\\olh\x6a"
+  "jtqvz"
+  "uzezxa\"jgbmojtwyfbfguz"
+  "vqsremfk\x8fxiknektafj"
+  "wzntebpxnnt\"vqndz\"i\x47vvjqo\""
+  "higvez\"k\"riewqk"
+  "dlkrbhbrlfrp\\damiauyucwhty"
+  "d\""
+  "qlz"
+  "ku"
+  "yy\"\"uoao\"uripabop"
+  "saduyrntuswlnlkuppdro\\sicxosted"
+  "tj"
+  "zzphopswlwdhebwkxeurvizdv"
+  "xfoheirjoakrpofles\"nfu"
+  "q\xb7oh\"p\xce\"n"
+  "qeendp\"ercwgywdjeylxcv"
+  "dcmem"
+  "\"i\x13r\"l"
+  "ikso\xdcbvqnbrjduh\"uqudzki\xderwk"
+  "wfdsn"
+  "pwynglklryhtsqbno"
+  "hcoj\x63iccz\"v\"ttr"
+  "zf\x23\\hlj\\kkce\\d\\asy\"yyfestwcdxyfj"
+  "xs"
+  "m\"tvltapxdvtrxiy"
+  "bmud"
+  "k\"a"
+  "b\"oas"
+  "\"yexnjjupoqsxyqnquy\"uzfdvetqrc"
+  "vdw\xe3olxfgujaj"
+  "qomcxdnd\"\\cfoe\""
+  "fpul"
+  "m\"avamefphkpv"
+  "vvdnb\\x\\uhnxfw\"dpubfkxfmeuhnxisd"
+  "hey\\"
+  "ldaeigghlfey"
+  "eure\"hoy\xa5iezjp\\tm"
+  "yygb\"twbj\\r\"\x10gmxuhmp\""
+  "weirebp\x39mqonbtmfmd"
+  "ltuz\\hs\"e"
+  "ysvmpc"
+  "g\x8amjtt\"megl\"omsaihifwa"
+  "yimmm"
+  "iiyqfalh"
+  "cwknlaaf"
+  "q\x37feg\xc6s\"xx"
+  "uayrgeurgyp\\oi"
+  "xhug\"pt\"axugllbdiggzhvy"
+  "kdaarqmsjfx\xc3d"
+  "\"vkwla"
+  "d\""
+  "tmroz\"bvfinxoe\\mum\"wmm"
+  "\"n\"bbswxne\\p\\yr\"qhwpdd"
+  "skzlkietklkqovjhvj\xfe"
+  "pbg\\pab\"bubqaf\"obzcwxwywbs\\dhtq"
+  "xxjidvqh\"lx\\wu\"ij"
+  "daef\x5fe\x5b\\kbeeb\x13qnydtboof"
+  "ogvazaqy\"j\x73"
+  "y"
+  "n\"tibetedldy\\gsamm\"nwu"
+  "wldkvgdtqulwkad"
+  "dpmxnj"
+  "twybw\"cdvf\"mjdajurokbce"
+  "ru\"\\lasij\"i"
+  "roc\\vra\\lhrm"
+  "pbkt\x60booz\"fjlkc"
+  "j\x4dytvjwrzt"
+  "\\uiwjkniumxcs"
+  "cbhm\"nexccior\"v\"j\"nazxilmfp\x47"
+  "qdxngevzrlgoq"
+  "\"lrzxftytpobsdfyrtdqpjbpuwmm\x9e"
+  "mdag\x0asnck\xc2ggj\"slb\"fjy"
+  "wyqkhjuazdtcgkcxvjkpnjdae"
+  "aixfk\xc0iom\x21vueob"
+  "dkiiakyjpkffqlluhaetires"
+  "ysspv\"lysgkvnmwbbsy"
+  "gy\"ryexcjjxdm\"xswssgtr"
+  "s"
+  "ddxv"
+  "qwt\"\x27puilb\"pslmbrsxhrz"
+  "qdg\xc9e\\qwtknlvkol\x54oqvmchn\\"
+  "lvo"
+  "b"
+  "fk\"aa\"\"yenwch\\\\on"
+  "srig\x63hpwaavs\\\x80qzk\"xa\"\xe6u\\wr"
+  "yxjxuj\"ghyhhxfj\"\xa6qvatre"
+  "yoktqxjxkzrklkoeroil"
+  "\"jfmik\""
+  "smgseztzdwldikbqrh\""
+  "jftahgctf\"hoqy"
+  "tcnhicr\"znpgckt\"ble"
+  "vqktnkodh\"lo\"a\\bkmdjqqnsqr"
+  "ztnirfzqq"
+  "s"
+  "xx"
+  "iqj\"y\\hqgzflwrdsusasekyrxbp\\ad"
+  "\\xzjhlaiynkioz\"\"bxepzimvgwt"
+  "s\x36rbw"
+  "mniieztwrisvdx"
+  "atyfxioy\x2b\\"
+  "irde\x85\x5cvbah\\jekw\"ia"
+  "bdmftlhkwrprmpat\"prfaocvp"
+  "w\\k"
+  "umbpausy"
+  "zfauhpsangy"
+  "p\"zqyw"
+  "wtztypyqvnnxzvlvipnq\"zu"
+  "deicgwq\\oqvajpbov\\or\"kgplwu"
+  "mbzlfgpi\\\\zqcidjpzqdzxityxa"
+  "lfkxvhma"
+  "\xf2yduqzqr\"\\fak\"p\"n"
+  "mpajacfuxotonpadvng"
+  "anb\\telzvcdu\\a\xf2flfq"
+  "lrs\"ebethwpmuuc\"\x86ygr"
+  "qmvdbhtumzc\"ci"
+  "meet"
+  "yopg\x0fdxdq\"h\\ugsu\xffmolxjv"
+  "uhy"
+  "fzgidrtzycsireghazscvmwcfmw\\t"
+  "cqohkhpgvpru"
+  "bihyigtnvmevx\"xx"
+  "xz"
+  "zofomwotzuxsjk\"q\"mc\"js\"dnmalhxd"
+  "\\ktnddux\\fqvt\"ibnjntjcbn"
+  "ia"
+  "htjadnefwetyp\xd5kbrwfycbyy"
+  "\"\\hkuxqddnao"
+  "meqqsz\x83luecpgaem"
+  "cvks\x87frvxo\"svqivqsdpgwhukmju"
+  "sgmxiai\\o\"riufxwjfigr\xdf"
+  "fgywdfecqufccpcdn"
+  "faghjoq\x28abxnpxj"
+  "zuppgzcfb\"dctvp\"elup\"zxkopx"
+  "xqs\x45xxdqcihbwghmzoa"
+  "anbnlp\\cgcvm\"hc"
+  "xf\"fgrngwzys"
+  "nrxsjduedcy\x24"
+  "\x71sxl\"gj\"sds\"ulcruguz\\t\\ssvjcwhi"
+  "jhj\"msch"
+  "qpovolktfwyiuyicbfeeju\x01"
+  "nkyxmb\"qyqultgt\"nmvzvvnxnb"
+  "ycsrkbstgzqb\"uv\\cisn"
+  "s"
+  "ueptjnn\"\"sh"
+  "lp\"z\"d\"mxtxiy"
+  "yzjtvockdnvbubqabjourf\"k\"uoxwle"
+  "\x82\"wqm\""
+  "\xb5cwtuks\x5fpgh"
+  "wd"
+  "tbvf"
+  "ttbmzdgn"
+  "vfpiyfdejyrlbgcdtwzbnm"
+  "uc"
+  "otdcmhpjagqix"
+  "\\\xb1qso\"s"
+  "scowax"
+  "behpstjdh\xccqlgnqjyz\"eesn"
+  "r\xe1cbnjwzveoomkzlo\\kxlfouhm"
+  "jgrl"
+  "kzqs\\r"
+  "ctscb\x7fthwkdyko\"\x62pkf\"d\xe6knmhurg"
+  "tc\"kw\x3ftt"
+  "bxb\x5ccl"
+  "jyrmfbphsldwpq"
+  "jylpvysl\"\"juducjg"
+  "en\\m\"kxpq\"wpb\\\""
+  "madouht\"bmdwvnyqvpnawiphgac\""
+  "vuxpk\"ltucrw"
+  "aae\x60arr"
+  "ttitnne\"kilkrgssnr\xfdurzh"
+  "oalw"
+  "pc\"\"gktkdykzbdpkwigucqni\"nxiqx"
+  "dbrsaj"
+  "bgzsowyxcbrvhtvekhsh\"qgd"
+  "kudfemvk\"\"\"hkbrbil\"chkqoa"
+  "zjzgj\\ekbhyfzufy"
+  "\\acos\"fqekuxqzxbmkbnn\x1ejzwrm"
+  "elxahvudn\"txtmomotgw"
+  "\x2eoxmwdhelpr\"cgi\xf7pzvb"
+  "eapheklx"
+  "hfvma\"mietvc\"tszbbm\"czex"
+  "h\"iiockj\\\xc1et"
+  "d\"rmjjftm"
+  "qlvhdcbqtyrhlc\\"
+  "yy\"rsucjtulm\"coryri\"eqjlbmk"
+  "tv"
+  "r\"bfuht\\jjgujp\""
+  "kukxvuauamtdosngdjlkauylttaokaj"
+  "srgost\"\"rbkcqtlccu\x65ohjptstrjkzy"
+  "yxwxl\\yjilwwxffrjjuazmzjs"
+  "dxlw\\fkstu\"hjrtiafhyuoh\"sewabne"
+  "\x88sj\"v"
+  "rfzprz\xec\"oxqclu\"krzefp\\q"
+  "cfmhdbjuhrcymgxpylllyvpni"
+  "ucrmjvmimmcq\x88\xd9\"lz"
+  "lujtt\""
+  "gvbqoixn\"pmledpjmo\"flydnwkfxllf"
+  "dvxqlbshhmelsk\x8big\"l"
+  "mx\x54lma\x8bbguxejg"
+  "\x66jdati\xeceieo"
+  "\"iyyupixei\x54ff"
+  "xohzf\"rbxsoksxamiu"
+  "vlhthspeshzbppa\x4drhqnohjop\"\"mfjd"
+  "f\"tvxxla\"vurian\"\"idjq\x3aptm\xc3olep"
+  "gzqz"
+  "kbq\\wogye\\altvi\\hbvmodny"
+  "j\xd8"
+  "ofjozdhkblvndl"
+  "hbitoupimbawimxlxqze"
+  "ypeleimnme"
+  "xfwdrzsc\\oxqamawyizvi\\y"
+  "enoikppx\xa1ixe\"yo\"gumye"
+  "fb"
+  "vzf"
+  "zxidr"
+  "cu\x31beirsywtskq"
+  "lxpjbvqzztafwezd"
+  "\\jyxeuo\x18bv"
+  "b\"vawc\"p\\\\giern\"b"
+  "odizunx\"\"t\\yicdn\"x\"sdiz"
+  "\"\"tebrtsi"
+  "ctyzsxv\xa6pegfkwsi\"tgyltaakytccb"
+  "htxwbofchvmzbppycccliyik\xe5a"
+  "ggsslefamsklezqkrd"
+  "rcep\"fnimwvvdx\"l"
+  "zyrzlqmd\x12egvqs\\llqyie"
+  "\x07gsqyrr\\rcyhyspsvn"
+  "butg\""
+  "gb"
+  "gywkoxf\"jsg\\wtopxvumirqxlwz"
+  "rj\"ir\"wldwveair\x2es\"dhjrdehbqnzl"
+  "ru\"elktnsbxufk\\ejufjfjlevt\\lrzd"
+  "\"widsvok"
+  "oy\"\x81nuesvw"
+  "ay"
+  "syticfac\x1cfjsivwlmy\"pumsqlqqzx"
+  "m"
+  "rjjkfh\x78cf\x2brgceg\"jmdyas\"\\xlv\xb6p"
+  "tmuvo\"\x3ffdqdovjmdmkgpstotojkv\"as"
+  "jd\\ojvynhxllfzzxvbn\"wrpphcvx"
+  "pz"
+  "\"twr"
+  "n\\hdzmxe\"mzjjeadlz"
+  "fb\"rprxuagvahjnri"
+  "rfmexmjjgh\\xrnmyvnatrvfruflaqjnd"
+  "obbbde\"co\"qr\"qpiwjgqahqm\\jjp\""
+  "vpbq\"\"y\"czk\\b\x52ed\"lnzepobp"
+  "syzeajzfarplydipny\"y\"\xe8ad"
+  "mpyodwb"
+  "\x47rakphlqqptd"
+  "wa\"oj\"aiy"
+  "a"
+  "ropozx"
+  "q\x51nbtlwa"
+  "etukvgx\\jqxlkq"
+  "\"tp\"rah\"pg\"s\"bpdtes\\tkasdhqd"
+  "dn\"qqpkikadowssb\xcah\"dzpsf\\ect\"jdh"
+  "pxunovbbrrn\\vullyn\"bno\"\"\"myfxlp\""
+  "qaixyazuryvkmoulhcqaotegfj\\mpzm"
+  "bvfrbicutzbjwn\\oml\"cf\"d\"ezcpv\"j"
+  "rmbrdtneudemigdhelmb"
+  "aq\\aurmbhy"
+  "wujqvzw"
+  "gf\"tssmvm\"gm\"hu\x9a\xb7yjawsa"
+  "hrhqqxow\xe2gsydtdspcfqy\"zw\\ou"
+  "ianwwf\\yko\\tdujhhqdi"
+  "xylz\"zpvpab"
+  "lwuopbeeegp"
+  "aoop\x49jhhcexdmdtun"
+  "\\\\mouqqcsgmz"
+  "tltuvwhveau\x43b\"ymxjlcgiymcynwt"
+  "gsugerumpyuhtjljbhrdyoj"
+  "lnjm\xb8wg\"ajh"
+  "zmspue\"nfttdon\\b\"eww"
+  "\"w\x67jwaq\x7ernmyvs\\rmdsuwydsd\"th"
+  "ogtgvtlmcvgllyv"
+  "z\"fqi\"rvddoehrciyl"
+  "yustxxtot\"muec\"xvfdbzunzvveq"
+  "mqslw"
+  "txqnyvzmibqgjs\xb6xy\x86nfalfyx"
+  "kzhehlmkholov"
+  "plpmywcnirrjutjguosh\\"
+  "pydbnqofv\"dn\\m"
+  "aegqof"
+  "eambmxt\\dxagoogl\\zapfwwlmk"
+  "afbmqitxxqhddlozuxcpjxgh"
+  "vgts"
+  "bfdpqtoxzzhmzcilehnflna"
+  "s\"idpz"
+  "\xcfhgly\"nlmztwybx\"ecezmsxaqw"
+  "aackfgndqcqiy"
+  "\x22unqdlsrvgzfaohoffgxzfpir\"s"
+  "abh\"ydv\"kbpdhrerl"
+  "bdzpg"
+  "ekwgkywtmzp"
+  "wtoodejqmrrgslhvnk\"pi\"ldnogpth"
+  "njro\x68qgbx\xe4af\"\\suan"
+#+END_EXAMPLE
+:END:
+
+#+BEGIN_SRC emacs-lisp :var input=8-input :exports both
+  (defun day8/hex-replacements (string-literal)
+    (-map (lambda (escaped-hex)
+            (let ((hex-code (string-to-number (substring escaped-hex 2) 16)))
+              (cons escaped-hex (char-to-string hex-code))))
+          (-map #'car (s-match-strings-all "\\\\x[0-9,a-f][0-9,a-f]" string-literal))))
+
+  (defun day8/parse-string (string-literal)
+    (let ((contents (substring string-literal 1 -1)))
+      (-reduce-from
+       (lambda (acc replacement)
+         (s-replace (car replacement)
+                    (cdr replacement)
+                    acc))
+       contents
+       (append '(("\\\"" . "\"")
+                 ("\\\\" . "\\"))
+               (day8/hex-replacements contents)))))
+
+  (ert-deftest day8/parse-string ()
+    (should (string-equal ""
+                          (day8/parse-string "\"\"")))
+    (should (string-equal "abc"
+                          (day8/parse-string "\"abc\"")))
+    (should (string-equal "aaa\"aaa"
+                          (day8/parse-string "\"aaa\\\"aaa\"")))
+    (should (string-equal "'"
+                          (day8/parse-string "\"\\x27\""))))
+
+
+  (let* ((code-strings (split-string input "\n" t))
+         (string-values (-map #'day8/parse-string code-strings)))
+    (- (-sum (-map #'length code-strings))
+       (-sum (-map #'length string-values))))
+#+END_SRC
+
+#+RESULTS[acaa7a9432ace3b411d0bfcd4c61620b43ce21c5]:
+: 1350
+