Day 3

diff --git a/advent_of_code_2020.jl b/advent_of_code_2020.jl
index df49843..9e8b81c 100644 (file)
--- a/advent_of_code_2020.jl
+++ b/advent_of_code_2020.jl
@@ -1,9 +1,17 @@
 ### A Pluto.jl notebook ###
-# v0.12.15
+# v0.12.16
 
 using Markdown
 using InteractiveUtils
 
+# ╔═╡ 661be9a0-353b-11eb-3598-a5b5245368cb
+html"""<style>
+main {
+       max-width: 100%;
+       margin-right: 0;
+}</style>
+"""
+
 # ╔═╡ f0dd4400-3313-11eb-3295-af913c2212fb
 md"# Advent Of Code 2020"
 
@@ -56,6 +64,15 @@ struct Password
        p :: String
 end    
 
+# ╔═╡ bbda1c1e-347a-11eb-0e7a-756906c4c9f4
+nb_of_valid_passwords_part2(passwords) =
+       count(
+               password ->
+                       (password.p[password.policy_range.start] == password.policy_char) ⊻
+                       (password.p[password.policy_range.stop] == password.policy_char),
+               passwords
+       )
+
 # ╔═╡ 10f5ffa0-3474-11eb-2a36-d5c6f78f18c6
 function parse_day2(lines)
        line_regexp = r"^(\d+)-(\d+) ([a-z]): ([a-z]+)$"
@@ -75,17 +92,7 @@ end
 # ╔═╡ 6695038e-3472-11eb-1846-3b1c041be59d
 nb_of_valid_passwords_part1(passwords) =
        count(
-               password ->
-                       count(==(password.policy_char), password.p) ∈ password.policy_range,
-               passwords
-       )
-
-# ╔═╡ bbda1c1e-347a-11eb-0e7a-756906c4c9f4
-nb_of_valid_passwords_part2(passwords) =
-       count(
-               password ->
-                       (password.p[password.policy_range.start] == password.policy_char) ⊻
-                       (password.p[password.policy_range.stop] == password.policy_char),
+               password -> count(==(password.policy_char), password.p) ∈ password.policy_range,
                passwords
        )
 
@@ -118,7 +125,65 @@ md"**Result for part 1**: $(nb_of_valid_passwords_part1(input_day2))"
 # ╔═╡ de3c2f00-347b-11eb-0aec-8b776a855f6a
 md"**Result for part 2**: $(nb_of_valid_passwords_part2(input_day2))"
 
+# ╔═╡ 14e39f60-3536-11eb-0c2a-5945a1ccb638
+md"## Day 3"
+
+# ╔═╡ 1b7ec110-3536-11eb-04c4-af7b43e6c68e
+function parse_day3(lines)     
+       map(==("#"), hcat(split.(lines, "")...))'
+end
+
+# ╔═╡ a6abdfc0-3536-11eb-3003-c13c39952d78
+function nb_trees_encountered(area :: AbstractArray{Bool, 2}, moves = [(1, 3)])
+       map(moves) do (di, dj)                                  
+               foldl(
+                       ((j, sum), i) -> (mod1(j + dj, size(area, 2)), sum + area[i, j]),
+                       1:di:size(area, 1),
+                       init = (1, 0)
+               )[2]
+       end
+end
+
+# ╔═╡ 1814fa70-353c-11eb-20de-51f779e98bdb
+nb_trees_encountered_part2(area) = nb_trees_encountered(area, [(1, 1), (1, 3), (1, 5), (1, 7), (2, 1)])
+
+# ╔═╡ da0fb260-3536-11eb-2c09-8f1b322090ab
+let
+       test_input = 
+        """..##.......
+               #...#...#..
+               .#....#..#.
+               ..#.#...#.#
+               .#...##..#.
+               ..#.##.....
+               .#.#.#....#
+               .#........#
+               #.##...#...
+               #...##....#
+               .#..#...#.#"""
+       trees = parse_day3(split(test_input, '\n'))
+       n_part1 = nb_trees_encountered(trees)   
+       n_part2 = nb_trees_encountered_part2(trees)
+       
+       md"
+Test 1, part 1: $(n_part1 == [7])
+
+Test 1, part 2: $(prod(n_part2) == 336)
+       "
+end
+
+# ╔═╡ c003a5ae-3537-11eb-00b2-e58a970471ac
+input_day3 = parse_day3(readlines("data/day03.txt"))
+
+# ╔═╡ ab7f3260-3539-11eb-3f97-fde10d5d852b
+md"
+**Result for part 1**: $(nb_trees_encountered(input_day3))
+
+**Result for part 2**: $(nb_trees_encountered_part2(input_day3) |> prod)
+"
+
 # ╔═╡ Cell order:
+# ╟─661be9a0-353b-11eb-3598-a5b5245368cb
 # ╟─f0dd4400-3313-11eb-3295-af913c2212fb
 # ╟─0b7b8920-3314-11eb-2cfb-7d20c0967e67
 # ╠═877b32e0-3315-11eb-0e96-650b19da693e
@@ -128,10 +193,17 @@ md"**Result for part 2**: $(nb_of_valid_passwords_part2(input_day2))"
 # ╟─c7dcdae0-33b1-11eb-2cab-fbc06c8ef76b
 # ╟─5d9712b0-3472-11eb-1423-719331dfe52f
 # ╠═b9144990-3473-11eb-0ba9-59f3fe6ddbc0
+# ╠═bbda1c1e-347a-11eb-0e7a-756906c4c9f4
 # ╠═10f5ffa0-3474-11eb-2a36-d5c6f78f18c6
 # ╠═6695038e-3472-11eb-1846-3b1c041be59d
-# ╠═bbda1c1e-347a-11eb-0e7a-756906c4c9f4
 # ╟─a0cfb670-3474-11eb-1a05-c12914658a0a
 # ╟─4a629040-347a-11eb-2aae-6f37a4c89168
 # ╟─5825aa50-347a-11eb-37ca-811e1b59d37a
 # ╟─de3c2f00-347b-11eb-0aec-8b776a855f6a
+# ╟─14e39f60-3536-11eb-0c2a-5945a1ccb638
+# ╠═1b7ec110-3536-11eb-04c4-af7b43e6c68e
+# ╠═a6abdfc0-3536-11eb-3003-c13c39952d78
+# ╠═1814fa70-353c-11eb-20de-51f779e98bdb
+# ╟─da0fb260-3536-11eb-2c09-8f1b322090ab
+# ╟─c003a5ae-3537-11eb-00b2-e58a970471ac
+# ╟─ab7f3260-3539-11eb-3f97-fde10d5d852b