Day 5 Preparation

chicken.org

@@ -2248,7 +2248,7 @@ actually been printed on the back of every card this whole time.
 There's no such thing as "points". Instead, scratchcards only cause you to *win more scratchcards*
 equal to the number of winning numbers you have.
 
-Specifically, you win copies of the scratchcards below the winning card equal to the number of
+Specifically, you win *copies* of the scratchcards below the winning card equal to the number of
 matches. So, if card 10 were to have 5 matching numbers, you would win one copy each of cards 11,
 12, 13, 14, and 15.
 
@@ -2362,6 +2362,8 @@ the original set of scratchcards, *how many total scratchcards do you end up wit
 
 ** Puzzle Input
 
+Jump to [[#headline-48][day 5]].
+
 #+NAME: day4-input
 #+begin_src fundamental
 Card   1: 33 56 23 64 92 86 94  7 59 13 | 86 92 64 43 10 70 16 55 79 33 56  8  7 25 82 14 31 96 94 13 99 29 69 75 23
@@ -2571,3 +2573,161 @@ Card 204: 23 75 70 14 95 84 61  9 66 77 | 79  8  1 64 50 41 32 93 58 15 33 10 28
 Card 205:  2 99 53 15 32  6 16 69 21 14 | 96 98 24 66  6 47  4 54 45 46 42 13 75 11 80 18 34 35 93 79 65 37 40 92 91
 Card 206: 74 30 29 66 68  2  3 34 79 87 | 63 45 88 78 98 27 97 32 38 75  9 11 71 93 55 69 56 20 12 82 81 41 80 23 94
 #+end_src
+
+
+* Day 5: If You Give A Seed A Fertilizer
+
+** Part One
+*** Quest
+You take the boat and find the gardener right where you were told he would be: managing a giant
+"garden" that looks more to you like a farm.
+
+"A water source? Island Island *is* the water source!" You point out that Snow Island isn't
+receiving any water.
+
+"Oh, we had to stop the water because we *ran out of sand* to [[https://en.wikipedia.org/wiki/Sand_filter][filter]] it with! Can't make snow with
+dirty water. Don't worry, I'm sure we'll get more sand soon; we only turned off the water a few
+days... weeks... oh no." His face sinks into a look of horrified realization.
+
+"I've been so busy making sure everyone here has food that I completely forgot to check why we
+stopped getting more sand! There's a ferry leaving soon that is headed over in that direction - it's
+much faster than your boat. Could you please go check it out?"
+
+You barely have time to agree to this request when he brings up another. "While you wait for the
+ferry, maybe you can help us with our *food production problem*. The latest Island Island [[https://en.wikipedia.org/wiki/Almanac][Almanac]]
+just arrived and we're having trouble making sense of it."
+
+The almanac (your puzzle input) lists all of the seeds that need to be planted. It also lists what
+type of soil to use with each kind of seed, what type of fertilizer to use with each kind of soil,
+what type of water to use with each kind of fertilizer, and so on. Every type of seed, soil,
+fertilizer and so on is identified with a number, but numbers are reused by each category - that is,
+soil =123= and fertilizer =123= aren't necessarily related to each other.
+
+For example:
+
+#+begin_example
+seeds: 79 14 55 13
+
+seed-to-soil map:
+50 98 2
+52 50 48
+
+soil-to-fertilizer map:
+0 15 37
+37 52 2
+39 0 15
+
+fertilizer-to-water map:
+49 53 8
+0 11 42
+42 0 7
+57 7 4
+
+water-to-light map:
+88 18 7
+18 25 70
+
+light-to-temperature map:
+45 77 23
+81 45 19
+68 64 13
+
+temperature-to-humidity map:
+0 69 1
+1 0 69
+
+humidity-to-location map:
+60 56 37
+56 93 4
+#+end_example
+
+The almanac starts by listing which seeds need to be planted: seeds =79=, =14=, =55=, and =13=.
+
+The rest of the almanac contains a list of *maps* which describe how to convert numbers from a
+*source category* into numbers in a *destination category*. That is, the section that starts with
+~seed-to-soil map:~ describes how to convert a *seed number* (the source) to a *soil number* (the
+destination). This lets the gardener and his team know which soil to use with which seeds, which
+water to use with which fertilizer, and so on.
+
+Rather than list every source number and its corresponding destination number one by one, the maps
+describe entire *ranges* of numbers that can be converted. Each line within a map contains three
+numbers: the *destination range start*, the *source range start*, and the *range length*.
+
+Consider again the example ~seed-to-soil map~:
+
+#+begin_example
+50 98 2
+52 50 48
+#+end_example
+
+The first line has a *destination range start* of =50=, a *source range start* of =98=, and a *range
+length* of =2=. This line means that the source range starts at =98= and contains two values: =98=
+and =99=. The destination range is the same length, but it starts at =50=, so its two values are
+=50= and =51=. With this information, you know that seed number =98= corresponds to soil number =50=
+and that seed number =99= corresponds to soil number =51=.
+
+The second line means that the source range starts at =50= and contains =48= values: =50=, =51=,
+..., =96=, =97=. This corresponds to a destination range starting at =52= and also containing =48=
+values: =52=, =53=, ..., =98=, =99=. So, seed number =53= corresponds to soil number =55=.
+
+Any source numbers that *aren't mapped* correspond to the *same* destination number. So, seed number
+=10= corresponds to soil number =10=.
+
+So, the entire list of seed numbers and their corresponding soil numbers looks like this:
+
+#+begin_example
+seed  soil
+0     0
+1     1
+...   ...
+48    48
+49    49
+50    52
+51    53
+...   ...
+96    98
+97    99
+98    50
+99    51
+#+end_example
+
+With this map, you can look up the soil number required for each initial seed number:
+
+- Seed number =79= corresponds to soil number =81=.
+- Seed number =14= corresponds to soil number =14=.
+- Seed number =55= corresponds to soil number =57=.
+- Seed number =13= corresponds to soil number =13=.
+
+The gardener and his team want to get started as soon as possible, so they'd like to know the
+closest location that needs a seed. Using these maps, find *the lowest location number that
+corresponds to any of the initial seeds*. To do this, you'll need to convert each seed number
+through other categories until you can find its corresponding *location number*. In this example,
+the corresponding types are:
+
+- Seed =79=, soil =81=, fertilizer =81=, water =81=, light =74=, temperature =78=, humidity =78=,
+ *location =82=*.
+- Seed =14=, soil =14=, fertilizer =53=, water =49=, light =42=, temperature =42=, humidity =43=,
+ *location =43=*.
+- Seed =55=, soil =57=, fertilizer =57=, water =53=, light =46=, temperature =82=, humidity =82=,
+ *location =86=*.
+- Seed =13=, soil =13=, fertilizer =52=, water =41=, light =34=, temperature =34=, humidity =35=,
+ *location =35=*.
+
+So, the lowest location number in this example is *=35=*.
+
+*What is the lowest location number that corresponds to any of the initial seed numbers?*
+
+*** Puzzle Solution
+
+#+begin_src scheme :exports none :noweb yes :tangle day5.scm
+  (import (chicken string)
+          (chicken irregex))
+  (define input "
+    <<day5-input>>
+    ")
+#+end_src
+
+TBD...
+
+** Part Two
+** Puzzle Input