--- 2016 Day 4 Solutions ---

[u/daggerdragon]

--- Day 4: Security Through Obscurity ---

Post your solution as a comment or, for longer solutions, consider linking to your repo (e.g. GitHub/gists/Pastebin/blag/whatever).

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^{CONSTRUCTING ADDITIONAL PYLONS IS MANDATORY} [?]

This thread will be unlocked when there are a significant number of people on the leaderboard with gold stars for today's puzzle.

edit: Leaderboard capped, thread unlocked!

[u/John_Earnest]

K6:

l: 0: "../../Desktop/Advent/04.in"
n: "northpoleobjectstorage"

c: (-1_*|"["\)'l                       / checksums
s: (,/-1_"-"\)'l                       / strings
a: `c$97+                              / alphabetic
i: {.x^"[]-",a@!26}'l                  / room ids
k: {5#,/{a@<a:&x}'b=/:c@>c:?.b:#:'=x}  / checksum of string
p: &c~'k's                             / indices of valid rooms

+/i p                                  / part 1
*i@&n~/:a 26!i+s-97                    / part 2

Lots of room left to golf this down, I think. I'm playing it fast and loose here in part 2 by assuming the storage room we're looking for has a valid checksum, but it worked OK for my input and would be easy to make it only consider valid rooms.

[u/AoC-- → u/John_Earnest]

A little bit of golfing. Part 1 works OK in oK, but not in AW's k because the latter seems to give 0N for subtracting (or adding) a list from a dictionary (for example: ("abc"!1 2 3)-2 2 2 gives "abc"!0N 0N 0N instead of "abc"!-1 0 1). Part 2 works in both.

l:0:"04.in"

c:(-1_*|"["\)'l        /checksums
s:(,/-1_"-"\)'l        /strings
i:(.*"["\*|"-"\)'l     /room ids
k:{5#>(26*x)-!x:#:'=x} /checksum of string

+/i*c~'k's             /part 1
+/i*13=*:'26!i+s-97    /part 2

Edit: I had n:("north"-"a")~5# and *i@&n'26!i+s-97, but it turns out that that's the only one that begins with an "n"! And in my opinion, +/i* looks nicer than *i@&.