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day 10

master
Dustin Swan 2 years ago
parent
commit
6541e2362a
  1. 73
      day10.ml
  2. 110
      day10.txt

73
day10.ml

@ -0,0 +1,73 @@
(* Common util. Should probably put this in a module or something.. *)
let get_one_line file =
try Some (input_line file) with
End_of_file -> None
let get_lines file =
let rec input lines =
match get_one_line file with
Some line -> input (line :: lines)
| None -> List.rev lines
in input []
let read_file file =
let channel = open_in(file) in
get_lines channel
let (>>) f g x = g(f(x))
let list_max l = List.fold_left (fun acc x -> if x > acc then x else acc) (List.hd l) l
let map_tuple f (a, b) = (f a, f b)
let memo_rec f =
let h = Hashtbl.create 1000 in
let rec g x =
try Hashtbl.find h x
with Not_found ->
let y = f g x in
Hashtbl.add h x y;
y
in g
(* --- *)
let rec collect_diffs = function
| x :: y :: [] -> [y - x] (* 2 elemnts left *)
| x :: y :: z -> y - x :: collect_diffs (y :: z)
let count_steps = (* returns a tuple of counts of 1's and 3's *)
List.partition (Int.equal 1)
>> map_tuple List.length
let count_valid self = function
| x :: y :: [] -> if y - x < 4 then 1 else 0
| x :: y :: rest ->
if y - x > 3
then 0
else self (x :: rest) + self (y :: rest)
let count_valid_memo = memo_rec count_valid
let () =
let lines = read_file "day10.txt"
|> List.map int_of_string
in
let adapter_jolts = 3 + list_max lines in
let sorted = lines
|> List.cons adapter_jolts (* add our adapter *)
|> List.cons 0 (* add the outlet *)
|> List.sort (fun x y -> if x > y then 1 else if x < y then -1 else 0)
in
sorted
|> collect_diffs
|> count_steps
|> fun (x, y) -> x * y
|> Printf.printf "prod: %i\n";
sorted
|> count_valid_memo
|> Printf.printf "\nsum: %i\n"

110
day10.txt

@ -0,0 +1,110 @@
160
34
123
159
148
93
165
56
179
103
171
44
110
170
147
98
25
37
137
71
5
6
121
28
19
134
18
7
66
90
88
181
89
41
156
46
8
61
124
9
161
72
13
172
111
59
105
51
109
27
152
117
52
68
95
164
116
75
78
180
81
47
104
12
133
175
16
149
135
99
112
38
67
53
153
2
136
113
17
145
106
31
45
169
146
168
26
36
118
62
65
142
130
1
140
84
94
141
122
22
48
102
60
178
127
73
74
87
182
35
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