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Day 04: Solution of part 1

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Original file line number	Diff line number	Diff line change
`@@ -12,4 +12,20 @@ not-a-real-room-404[oarel] is a real room.`
`12`	`12`	`totally-real-room-200[decoy] is not.`
`13`	`13`	`Of the real rooms from the list above, the sum of their sector IDs is 1514.`
`14`	`14`
`15`		`-What is the sum of the sector IDs of the real rooms?`
	`15`	`+What is the sum of the sector IDs of the real rooms?`
	`16`	`+`
	`17`	`+Your puzzle answer was 409147.`
	`18`	`+`
	`19`	`+The first half of this puzzle is complete! It provides one gold star: *`
	`20`	`+`
	`21`	`+--- Part Two ---`
	`22`	`+`
	`23`	`+With all the decoy data out of the way, it's time to decrypt this list and get moving.`
	`24`	`+`
	`25`	`+The room names are encrypted by a state-of-the-art shift cipher, which is nearly unbreakable without the right software. However, the information kiosk designers at Easter Bunny HQ were not expecting to deal with a master cryptographer like yourself.`
	`26`	`+`
	`27`	`+To decrypt a room name, rotate each letter forward through the alphabet a number of times equal to the room's sector ID. A becomes B, B becomes C, Z becomes A, and so on. Dashes become spaces.`
	`28`	`+`
	`29`	`+For example, the real name for qzmt-zixmtkozy-ivhz-343 is very encrypted name.`
	`30`	`+`
	`31`	`+What is the sector ID of the room where North Pole objects are stored?`

Lines changed: 26 additions & 0 deletions

Original file line number	Diff line number	Diff line change
`@@ -1,12 +1,38 @@`
`1`	`1`	`from lib import solution`
	`2`	`+import re`
	`3`	`+import collections`
	`4`	`+import operator`
`2`	`5`
`3`	`6`
`4`	`7`	`class Solution(solution.Solution):`
`5`	`8`	`def __init__(self, nr):`
`6`	`9`	`super().__init__(nr)`
	`10`	`+ self.sum1 = 0`
`7`	`11`
`8`	`12`	`def calculate(self, test=False):`
`9`	`13`	`self.read_instructions()`
	`14`	`+ self.calc_part1()`
`10`	`15`
`11`	`16`	`def read_instructions(self):`
`12`	`17`	`self.read_input(True)`
	`18`	`+`
	`19`	`+ def calc_part1(self):`
	`20`	`+ for line in self.input:`
	`21`	`+ match = re.match('([a-z\-]+)-(\d+)\[([a-z]{5})\]', line)`
	`22`	`+ if match:`
	`23`	`+ name = match.group(1)`
	`24`	`+ sector_id = match.group(2)`
	`25`	`+ checksum = match.group(3)`
	`26`	`+ if self.get_checksum(name) == checksum:`
	`27`	`+ self.sum1 += int(sector_id)`
	`28`	`+ self.set_solution(1, self.sum1)`
	`29`	`+`
	`30`	`+ @staticmethod`
	`31`	`+ def get_checksum(name):`
	`32`	`+ d = collections.defaultdict(int)`
	`33`	`+ for c in name:`
	`34`	`+ if c.isalpha():`
	`35`	`+ d[c] -= 1`
	`36`	`+ s = collections.OrderedDict(sorted(d.items(), key=operator.itemgetter(1, 0)))`
	`37`	`+ checksum = "".join(str(x) for x in s)[:5]`
	`38`	`+ return checksum`

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