solve some 2015 problems

2015/.envrc

@@ -0,0 +1 @@
+export ADVENT_OF_CODE_SESSION=53616c7465645f5f92dfbc249005a7e94ec3c6e62cd4e5e9ddf8e368a48c0c80440b6c5e37d836cc0b294e19a9e8a7f1

2015/.formatter.exs

@@ -0,0 +1,4 @@
+# Used by "mix format"
+[
+  inputs: ["{mix,.formatter}.exs", "{config,lib,test}/**/*.{ex,exs}"]
+]

2015/.gitignore

@@ -0,0 +1,26 @@
+# The directory Mix will write compiled artifacts to.
+/_build/
+
+# If you run "mix test --cover", coverage assets end up here.
+/cover/
+
+# The directory Mix downloads your dependencies sources to.
+/deps/
+
+# Where third-party dependencies like ExDoc output generated docs.
+/doc/
+
+# Ignore .fetch files in case you like to edit your project deps locally.
+/.fetch
+
+# If the VM crashes, it generates a dump, let's ignore it too.
+erl_crash.dump
+
+# Also ignore archive artifacts (built via "mix archive.build").
+*.ez
+
+# Ignore package tarball (built via "mix hex.build").
+advent_of_code_2015-*.tar
+
+# Temporary files, for example, from tests.
+/tmp/

2015/.iex.exs

@@ -0,0 +1 @@
+import AOC.IEx

2015/.tool-versions

@@ -0,0 +1,2 @@
+erlang 24.1.4
+elixir 1.12.3-otp-24

2015/README.md

@@ -0,0 +1,20 @@
+# Advent of Code 2015
+
+<details>
+  <summary>Setup</summary>
+
+  Using [asdf](https://asdf-vm.com/#/):
+
+  ```sh
+  asdf plugin add erlang
+  asdf plugin add elixir
+  asdf install
+  ```
+</details>
+
+|  S  |  M  |  T  |  W  |  T  |  F  |  S  |
+| :-: | :-: | :-: | :-: | :-: | :-: | :-: |
+|     |     |  1  |  2  |  3  |  4  |  5  |
+|  6  |  7  |  8  |  9  |  10 | 11  | 12  |
+| 13  | 14  | 15  | 16  | 17  | 18  | 19  |
+| 20  | 21  | 22  | 23  | 24  | 25  |     |

2015/config/config.exs

@@ -0,0 +1,8 @@
+import Config
+
+config :nx, :default_defn_options, compiler: EXLA
+
+config :advent_of_code_utils,
+  year: 2015,
+  auto_reload?: true,
+  session: System.get_env("ADVENT_OF_CODE_SESSION")

2015/input/2015_4.txt

@@ -0,0 +1 @@
+ckczppom

2015/input/2015_6.txt

@@ -0,0 +1,300 @@
+turn on 489,959 through 759,964
+turn off 820,516 through 871,914
+turn off 427,423 through 929,502
+turn on 774,14 through 977,877
+turn on 410,146 through 864,337
+turn on 931,331 through 939,812
+turn off 756,53 through 923,339
+turn off 313,787 through 545,979
+turn off 12,823 through 102,934
+toggle 756,965 through 812,992
+turn off 743,684 through 789,958
+toggle 120,314 through 745,489
+toggle 692,845 through 866,994
+turn off 587,176 through 850,273
+turn off 674,321 through 793,388
+toggle 749,672 through 973,965
+turn on 943,30 through 990,907
+turn on 296,50 through 729,664
+turn on 212,957 through 490,987
+toggle 171,31 through 688,88
+turn off 991,989 through 994,998
+turn off 913,943 through 958,953
+turn off 278,258 through 367,386
+toggle 275,796 through 493,971
+turn off 70,873 through 798,923
+toggle 258,985 through 663,998
+turn on 601,259 through 831,486
+turn off 914,94 through 941,102
+turn off 558,161 through 994,647
+turn on 119,662 through 760,838
+toggle 378,775 through 526,852
+turn off 384,670 through 674,972
+turn off 249,41 through 270,936
+turn on 614,742 through 769,780
+turn on 427,70 through 575,441
+turn on 410,478 through 985,753
+turn off 619,46 through 931,342
+turn on 284,55 through 768,922
+turn off 40,592 through 728,685
+turn on 825,291 through 956,950
+turn on 147,843 through 592,909
+turn off 218,675 through 972,911
+toggle 249,291 through 350,960
+turn off 556,80 through 967,675
+toggle 609,148 through 968,279
+toggle 217,605 through 961,862
+toggle 407,177 through 548,910
+toggle 400,936 through 599,938
+turn off 721,101 through 925,455
+turn on 268,631 through 735,814
+toggle 549,969 through 612,991
+toggle 553,268 through 689,432
+turn off 817,668 through 889,897
+toggle 801,544 through 858,556
+toggle 615,729 through 832,951
+turn off 427,477 through 958,948
+turn on 164,49 through 852,946
+turn on 542,449 through 774,776
+turn off 923,196 through 980,446
+toggle 90,310 through 718,846
+turn off 657,215 through 744,252
+turn off 800,239 through 811,712
+turn on 502,90 through 619,760
+toggle 649,512 through 862,844
+turn off 334,903 through 823,935
+turn off 630,233 through 839,445
+turn on 713,67 through 839,865
+turn on 932,50 through 982,411
+turn off 480,729 through 984,910
+turn on 100,219 through 796,395
+turn on 758,108 through 850,950
+turn off 427,276 through 439,938
+turn on 178,284 through 670,536
+toggle 540,27 through 625,102
+turn off 906,722 through 936,948
+toggle 345,418 through 859,627
+toggle 175,775 through 580,781
+toggle 863,28 through 929,735
+turn off 824,858 through 905,973
+toggle 752,312 through 863,425
+turn on 985,716 through 988,852
+turn off 68,504 through 763,745
+toggle 76,209 through 810,720
+turn off 657,607 through 676,664
+toggle 596,869 through 896,921
+turn off 915,411 through 968,945
+turn off 368,39 through 902,986
+turn on 11,549 through 393,597
+turn off 842,893 through 976,911
+toggle 274,106 through 581,329
+toggle 406,403 through 780,950
+toggle 408,988 through 500,994
+toggle 217,73 through 826,951
+turn on 917,872 through 961,911
+toggle 394,34 through 510,572
+toggle 424,603 through 583,626
+toggle 106,159 through 755,738
+turn off 244,610 through 472,709
+turn on 350,265 through 884,690
+turn on 688,184 through 928,280
+toggle 279,443 through 720,797
+turn off 615,493 through 888,610
+toggle 118,413 through 736,632
+turn on 798,782 through 829,813
+turn off 250,934 through 442,972
+turn on 68,503 through 400,949
+toggle 297,482 through 313,871
+toggle 710,3 through 839,859
+turn on 125,300 through 546,888
+toggle 482,39 through 584,159
+turn off 536,89 through 765,962
+turn on 530,518 through 843,676
+turn on 994,467 through 994,676
+turn on 623,628 through 744,927
+toggle 704,912 through 837,983
+turn on 154,364 through 517,412
+toggle 344,409 through 780,524
+turn off 578,740 through 725,879
+turn on 251,933 through 632,957
+turn on 827,705 through 971,789
+toggle 191,282 through 470,929
+toggle 324,525 through 446,867
+toggle 534,343 through 874,971
+toggle 550,650 through 633,980
+toggle 837,404 through 881,915
+toggle 338,881 through 845,905
+turn on 469,462 through 750,696
+turn on 741,703 through 892,870
+turn off 570,215 through 733,562
+turn on 445,576 through 870,775
+turn on 466,747 through 554,878
+turn off 820,453 through 868,712
+turn off 892,706 through 938,792
+turn off 300,238 through 894,746
+turn off 306,44 through 457,444
+turn off 912,569 through 967,963
+toggle 109,756 through 297,867
+turn on 37,546 through 41,951
+turn on 321,637 through 790,910
+toggle 66,50 through 579,301
+toggle 933,221 through 933,791
+turn on 486,676 through 878,797
+turn on 417,231 through 556,317
+toggle 904,468 through 981,873
+turn on 417,675 through 749,712
+turn on 692,371 through 821,842
+toggle 324,73 through 830,543
+turn on 912,490 through 977,757
+turn off 634,872 through 902,949
+toggle 266,779 through 870,798
+turn on 772,982 through 990,996
+turn off 607,46 through 798,559
+turn on 295,602 through 963,987
+turn on 657,86 through 944,742
+turn off 334,639 through 456,821
+turn off 997,667 through 997,670
+turn off 725,832 through 951,945
+turn off 30,120 through 952,984
+turn on 860,965 through 917,976
+toggle 471,997 through 840,998
+turn off 319,307 through 928,504
+toggle 823,631 through 940,908
+toggle 969,984 through 981,993
+turn off 691,319 through 865,954
+toggle 911,926 through 938,929
+turn on 953,937 through 968,991
+toggle 914,643 through 975,840
+turn on 266,982 through 436,996
+turn off 101,896 through 321,932
+turn off 193,852 through 751,885
+turn off 576,532 through 863,684
+turn on 761,456 through 940,783
+turn on 20,290 through 398,933
+turn off 435,335 through 644,652
+turn on 830,569 through 905,770
+turn off 630,517 through 905,654
+turn on 664,53 through 886,976
+toggle 275,416 through 408,719
+turn on 370,621 through 515,793
+turn on 483,373 through 654,749
+turn on 656,786 through 847,928
+turn off 532,752 through 945,974
+toggle 301,150 through 880,792
+turn off 951,488 through 958,952
+turn on 207,729 through 882,828
+toggle 694,532 through 973,961
+toggle 676,639 through 891,802
+turn off 653,6 through 905,519
+toggle 391,109 through 418,312
+turn on 877,423 through 957,932
+turn on 340,145 through 563,522
+turn off 978,467 through 988,895
+turn off 396,418 through 420,885
+turn off 31,308 through 816,316
+turn on 107,675 through 758,824
+turn on 61,82 through 789,876
+turn on 750,743 through 754,760
+toggle 88,733 through 736,968
+turn off 754,349 through 849,897
+toggle 157,50 through 975,781
+turn off 230,231 through 865,842
+turn off 516,317 through 630,329
+turn off 697,820 through 829,903
+turn on 218,250 through 271,732
+toggle 56,167 through 404,431
+toggle 626,891 through 680,927
+toggle 370,207 through 791,514
+toggle 860,74 through 949,888
+turn on 416,527 through 616,541
+turn off 745,449 through 786,908
+turn on 485,554 through 689,689
+turn on 586,62 through 693,141
+toggle 506,759 through 768,829
+turn on 473,109 through 929,166
+turn on 760,617 through 773,789
+toggle 595,683 through 618,789
+turn off 210,775 through 825,972
+toggle 12,426 through 179,982
+turn on 774,539 through 778,786
+turn on 102,498 through 121,807
+turn off 706,897 through 834,965
+turn off 678,529 through 824,627
+turn on 7,765 through 615,870
+turn off 730,872 through 974,943
+turn off 595,626 through 836,711
+turn off 215,424 through 841,959
+toggle 341,780 through 861,813
+toggle 507,503 through 568,822
+turn on 252,603 through 349,655
+toggle 93,521 through 154,834
+turn on 565,682 through 951,954
+turn on 544,318 through 703,418
+toggle 756,953 through 891,964
+turn on 531,123 through 856,991
+turn on 148,315 through 776,559
+turn off 925,835 through 963,971
+turn on 895,944 through 967,964
+turn off 102,527 through 650,747
+toggle 626,105 through 738,720
+turn off 160,75 through 384,922
+toggle 813,724 through 903,941
+turn on 207,107 through 982,849
+toggle 750,505 through 961,697
+toggle 105,410 through 885,819
+turn on 226,104 through 298,283
+turn off 224,604 through 508,762
+turn on 477,368 through 523,506
+turn off 477,901 through 627,936
+turn off 887,131 through 889,670
+turn on 896,994 through 938,999
+toggle 401,580 through 493,728
+toggle 987,184 through 991,205
+turn on 821,643 through 882,674
+toggle 784,940 through 968,959
+turn off 251,293 through 274,632
+turn off 339,840 through 341,844
+turn off 675,351 through 675,836
+toggle 918,857 through 944,886
+toggle 70,253 through 918,736
+turn off 612,604 through 772,680
+turn off 277,40 through 828,348
+toggle 692,139 through 698,880
+toggle 124,446 through 883,453
+toggle 969,932 through 990,945
+toggle 855,692 through 993,693
+toggle 722,472 through 887,899
+toggle 978,149 through 985,442
+toggle 837,540 through 916,889
+turn off 612,2 through 835,82
+toggle 560,767 through 878,856
+turn on 461,734 through 524,991
+toggle 206,824 through 976,912
+turn on 826,610 through 879,892
+turn on 577,699 through 956,933
+turn off 9,250 through 50,529
+turn off 77,657 through 817,677
+turn on 68,419 through 86,426
+turn on 991,720 through 992,784
+turn on 668,20 through 935,470
+turn off 133,418 through 613,458
+turn off 487,286 through 540,328
+toggle 247,874 through 840,955
+toggle 301,808 through 754,970
+turn off 34,194 through 578,203
+turn off 451,49 through 492,921
+turn on 907,256 through 912,737
+turn off 479,305 through 702,587
+turn on 545,583 through 732,749
+toggle 11,16 through 725,868
+turn on 965,343 through 986,908
+turn on 674,953 through 820,965
+toggle 398,147 through 504,583
+turn off 778,194 through 898,298
+turn on 179,140 through 350,852
+turn off 241,118 through 530,832
+turn off 41,447 through 932,737
+turn off 820,663 through 832,982
+turn on 550,460 through 964,782
+turn on 31,760 through 655,892
+toggle 628,958 through 811,992

2015/input/2015_7.txt

@@ -0,0 +1,339 @@
+af AND ah -> ai
+NOT lk -> ll
+hz RSHIFT 1 -> is
+NOT go -> gp
+du OR dt -> dv
+x RSHIFT 5 -> aa
+at OR az -> ba
+eo LSHIFT 15 -> es
+ci OR ct -> cu
+b RSHIFT 5 -> f
+fm OR fn -> fo
+NOT ag -> ah
+v OR w -> x
+g AND i -> j
+an LSHIFT 15 -> ar
+1 AND cx -> cy
+jq AND jw -> jy
+iu RSHIFT 5 -> ix
+gl AND gm -> go
+NOT bw -> bx
+jp RSHIFT 3 -> jr
+hg AND hh -> hj
+bv AND bx -> by
+er OR es -> et
+kl OR kr -> ks
+et RSHIFT 1 -> fm
+e AND f -> h
+u LSHIFT 1 -> ao
+he RSHIFT 1 -> hx
+eg AND ei -> ej
+bo AND bu -> bw
+dz OR ef -> eg
+dy RSHIFT 3 -> ea
+gl OR gm -> gn
+da LSHIFT 1 -> du
+au OR av -> aw
+gj OR gu -> gv
+eu OR fa -> fb
+lg OR lm -> ln
+e OR f -> g
+NOT dm -> dn
+NOT l -> m
+aq OR ar -> as
+gj RSHIFT 5 -> gm
+hm AND ho -> hp
+ge LSHIFT 15 -> gi
+jp RSHIFT 1 -> ki
+hg OR hh -> hi
+lc LSHIFT 1 -> lw
+km OR kn -> ko
+eq LSHIFT 1 -> fk
+1 AND am -> an
+gj RSHIFT 1 -> hc
+aj AND al -> am
+gj AND gu -> gw
+ko AND kq -> kr
+ha OR gz -> hb
+bn OR by -> bz
+iv OR jb -> jc
+NOT ac -> ad
+bo OR bu -> bv
+d AND j -> l
+bk LSHIFT 1 -> ce
+de OR dk -> dl
+dd RSHIFT 1 -> dw
+hz AND ik -> im
+NOT jd -> je
+fo RSHIFT 2 -> fp
+hb LSHIFT 1 -> hv
+lf RSHIFT 2 -> lg
+gj RSHIFT 3 -> gl
+ki OR kj -> kk
+NOT ak -> al
+ld OR le -> lf
+ci RSHIFT 3 -> ck
+1 AND cc -> cd
+NOT kx -> ky
+fp OR fv -> fw
+ev AND ew -> ey
+dt LSHIFT 15 -> dx
+NOT ax -> ay
+bp AND bq -> bs
+NOT ii -> ij
+ci AND ct -> cv
+iq OR ip -> ir
+x RSHIFT 2 -> y
+fq OR fr -> fs
+bn RSHIFT 5 -> bq
+0 -> c
+14146 -> b
+d OR j -> k
+z OR aa -> ab
+gf OR ge -> gg
+df OR dg -> dh
+NOT hj -> hk
+NOT di -> dj
+fj LSHIFT 15 -> fn
+lf RSHIFT 1 -> ly
+b AND n -> p
+jq OR jw -> jx
+gn AND gp -> gq
+x RSHIFT 1 -> aq
+ex AND ez -> fa
+NOT fc -> fd
+bj OR bi -> bk
+as RSHIFT 5 -> av
+hu LSHIFT 15 -> hy
+NOT gs -> gt
+fs AND fu -> fv
+dh AND dj -> dk
+bz AND cb -> cc
+dy RSHIFT 1 -> er
+hc OR hd -> he
+fo OR fz -> ga
+t OR s -> u
+b RSHIFT 2 -> d
+NOT jy -> jz
+hz RSHIFT 2 -> ia
+kk AND kv -> kx
+ga AND gc -> gd
+fl LSHIFT 1 -> gf
+bn AND by -> ca
+NOT hr -> hs
+NOT bs -> bt
+lf RSHIFT 3 -> lh
+au AND av -> ax
+1 AND gd -> ge
+jr OR js -> jt
+fw AND fy -> fz
+NOT iz -> ja
+c LSHIFT 1 -> t
+dy RSHIFT 5 -> eb
+bp OR bq -> br
+NOT h -> i
+1 AND ds -> dt
+ab AND ad -> ae
+ap LSHIFT 1 -> bj
+br AND bt -> bu
+NOT ca -> cb
+NOT el -> em
+s LSHIFT 15 -> w
+gk OR gq -> gr
+ff AND fh -> fi
+kf LSHIFT 15 -> kj
+fp AND fv -> fx
+lh OR li -> lj
+bn RSHIFT 3 -> bp
+jp OR ka -> kb
+lw OR lv -> lx
+iy AND ja -> jb
+dy OR ej -> ek
+1 AND bh -> bi
+NOT kt -> ku
+ao OR an -> ap
+ia AND ig -> ii
+NOT ey -> ez
+bn RSHIFT 1 -> cg
+fk OR fj -> fl
+ce OR cd -> cf
+eu AND fa -> fc
+kg OR kf -> kh
+jr AND js -> ju
+iu RSHIFT 3 -> iw
+df AND dg -> di
+dl AND dn -> do
+la LSHIFT 15 -> le
+fo RSHIFT 1 -> gh
+NOT gw -> gx
+NOT gb -> gc
+ir LSHIFT 1 -> jl
+x AND ai -> ak
+he RSHIFT 5 -> hh
+1 AND lu -> lv
+NOT ft -> fu
+gh OR gi -> gj
+lf RSHIFT 5 -> li
+x RSHIFT 3 -> z
+b RSHIFT 3 -> e
+he RSHIFT 2 -> hf
+NOT fx -> fy
+jt AND jv -> jw
+hx OR hy -> hz
+jp AND ka -> kc
+fb AND fd -> fe
+hz OR ik -> il
+ci RSHIFT 1 -> db
+fo AND fz -> gb
+fq AND fr -> ft
+gj RSHIFT 2 -> gk
+cg OR ch -> ci
+cd LSHIFT 15 -> ch
+jm LSHIFT 1 -> kg
+ih AND ij -> ik
+fo RSHIFT 3 -> fq
+fo RSHIFT 5 -> fr
+1 AND fi -> fj
+1 AND kz -> la
+iu AND jf -> jh
+cq AND cs -> ct
+dv LSHIFT 1 -> ep
+hf OR hl -> hm
+km AND kn -> kp
+de AND dk -> dm
+dd RSHIFT 5 -> dg
+NOT lo -> lp
+NOT ju -> jv
+NOT fg -> fh
+cm AND co -> cp
+ea AND eb -> ed
+dd RSHIFT 3 -> df
+gr AND gt -> gu
+ep OR eo -> eq
+cj AND cp -> cr
+lf OR lq -> lr
+gg LSHIFT 1 -> ha
+et RSHIFT 2 -> eu
+NOT jh -> ji
+ek AND em -> en
+jk LSHIFT 15 -> jo
+ia OR ig -> ih
+gv AND gx -> gy
+et AND fe -> fg
+lh AND li -> lk
+1 AND io -> ip
+kb AND kd -> ke
+kk RSHIFT 5 -> kn
+id AND if -> ig
+NOT ls -> lt
+dw OR dx -> dy
+dd AND do -> dq
+lf AND lq -> ls
+NOT kc -> kd
+dy AND ej -> el
+1 AND ke -> kf
+et OR fe -> ff
+hz RSHIFT 5 -> ic
+dd OR do -> dp
+cj OR cp -> cq
+NOT dq -> dr
+kk RSHIFT 1 -> ld
+jg AND ji -> jj
+he OR hp -> hq
+hi AND hk -> hl
+dp AND dr -> ds
+dz AND ef -> eh
+hz RSHIFT 3 -> ib
+db OR dc -> dd
+hw LSHIFT 1 -> iq
+he AND hp -> hr
+NOT cr -> cs
+lg AND lm -> lo
+hv OR hu -> hw
+il AND in -> io
+NOT eh -> ei
+gz LSHIFT 15 -> hd
+gk AND gq -> gs
+1 AND en -> eo
+NOT kp -> kq
+et RSHIFT 5 -> ew
+lj AND ll -> lm
+he RSHIFT 3 -> hg
+et RSHIFT 3 -> ev
+as AND bd -> bf
+cu AND cw -> cx
+jx AND jz -> ka
+b OR n -> o
+be AND bg -> bh
+1 AND ht -> hu
+1 AND gy -> gz
+NOT hn -> ho
+ck OR cl -> cm
+ec AND ee -> ef
+lv LSHIFT 15 -> lz
+ks AND ku -> kv
+NOT ie -> if
+hf AND hl -> hn
+1 AND r -> s
+ib AND ic -> ie
+hq AND hs -> ht
+y AND ae -> ag
+NOT ed -> ee
+bi LSHIFT 15 -> bm
+dy RSHIFT 2 -> dz
+ci RSHIFT 2 -> cj
+NOT bf -> bg
+NOT im -> in
+ev OR ew -> ex
+ib OR ic -> id
+bn RSHIFT 2 -> bo
+dd RSHIFT 2 -> de
+bl OR bm -> bn
+as RSHIFT 1 -> bl
+ea OR eb -> ec
+ln AND lp -> lq
+kk RSHIFT 3 -> km
+is OR it -> iu
+iu RSHIFT 2 -> iv
+as OR bd -> be
+ip LSHIFT 15 -> it
+iw OR ix -> iy
+kk RSHIFT 2 -> kl
+NOT bb -> bc
+ci RSHIFT 5 -> cl
+ly OR lz -> ma
+z AND aa -> ac
+iu RSHIFT 1 -> jn
+cy LSHIFT 15 -> dc
+cf LSHIFT 1 -> cz
+as RSHIFT 3 -> au
+cz OR cy -> da
+kw AND ky -> kz
+lx -> a
+iw AND ix -> iz
+lr AND lt -> lu
+jp RSHIFT 5 -> js
+aw AND ay -> az
+jc AND je -> jf
+lb OR la -> lc
+NOT cn -> co
+kh LSHIFT 1 -> lb
+1 AND jj -> jk
+y OR ae -> af
+ck AND cl -> cn
+kk OR kv -> kw
+NOT cv -> cw
+kl AND kr -> kt
+iu OR jf -> jg
+at AND az -> bb
+jp RSHIFT 2 -> jq
+iv AND jb -> jd
+jn OR jo -> jp
+x OR ai -> aj
+ba AND bc -> bd
+jl OR jk -> jm
+b RSHIFT 1 -> v
+o AND q -> r
+NOT p -> q
+k AND m -> n
+as RSHIFT 2 -> at

2015/lib/2015/1.ex

@@ -0,0 +1,26 @@
+import AOC
+
+aoc 2015, 1 do
+  def input_chars(), do: input_string() |> String.split("", trim: true)
+
+  def p1 do
+    input_chars()
+    |> Enum.reduce(0, fn
+      "(", floor -> floor + 1
+      ")", floor -> floor - 1
+    end)
+  end
+
+  def p2 do
+    input_string()
+    |> find_step_entering_basement(0, 0)
+  end
+
+  defp find_step_entering_basement(")" <> _, 0, step), do: step + 1
+
+  defp find_step_entering_basement("(" <> rest, floor, step),
+    do: find_step_entering_basement(rest, floor + 1, step + 1)
+
+  defp find_step_entering_basement(")" <> rest, floor, step),
+    do: find_step_entering_basement(rest, floor - 1, step + 1)
+end

2015/lib/2015/2.ex

@@ -0,0 +1,32 @@
+import AOC
+
+aoc 2015, 2 do
+  def dimensions_stream(),
+    do:
+      input_stream()
+      |> Stream.map(fn line ->
+        [l, w, h] = String.split(line, "x") |> Enum.map(&String.to_integer/1)
+        {l, w, h}
+      end)
+
+  def p1 do
+    dimensions_stream()
+    |> Stream.map(fn {l, w, h} ->
+      a = l * w
+      b = w * h
+      c = h * l
+      2 * a + 2 * b + 2 * c + Enum.min([a, b, c])
+    end)
+    |> Enum.sum()
+  end
+
+  def p2 do
+    dimensions_stream()
+    |> Stream.map(fn {l, w, h} ->
+      [x, y | _] = Enum.sort([l, w, h])
+
+      2 * x + 2 * y + l * w * h
+    end)
+    |> Enum.sum()
+  end
+end

2015/lib/2015/3.ex

@@ -0,0 +1,46 @@
+import AOC
+
+aoc 2015, 3 do
+  def input_chars(), do: input_string() |> String.split("", trim: true)
+
+  def p1 do
+    input_chars()
+    |> run()
+    |> then(fn {visited, _} -> MapSet.size(visited) end)
+  end
+
+  def p2 do
+    {santa, robo_santa} =
+      input_chars()
+      |> Enum.with_index()
+      |> Enum.split_with(fn {_, i} -> Integer.mod(i, 2) == 0 end)
+      |> then(fn {santa, robo_santa} ->
+        {without_index(santa), without_index(robo_santa)}
+      end)
+
+    {visited, _} = run(santa)
+    {visited, _} = run(robo_santa, visited)
+
+    MapSet.size(visited)
+  end
+
+  defp op("^"), do: {1, 0}
+  defp op(">"), do: {0, 1}
+  defp op("v"), do: {-1, 0}
+  defp op("<"), do: {0, -1}
+
+  defp add({x, y}, {a, b}), do: {x + a, y + b}
+
+  defp run(inst, visited \\ MapSet.new()) do
+    starting_position = {0, 0}
+    visited = MapSet.put(visited, starting_position)
+
+    Enum.reduce(inst, {visited, starting_position}, fn command, {visited, current_position} ->
+      current_position = add(current_position, op(command))
+      visited = MapSet.put(visited, current_position)
+      {visited, current_position}
+    end)
+  end
+
+  defp without_index(enum), do: Enum.map(enum, &elem(&1, 0))
+end

2015/lib/2015/4.ex

@@ -0,0 +1,31 @@
+import AOC
+
+aoc 2015, 4 do
+  def p1 do
+    input_string()
+    |> String.trim()
+    |> mine_advent_coin(5)
+  end
+
+  defp mine_advent_coin(key, difficulty, nonce \\ 0)
+
+  defp mine_advent_coin(key, 5, nonce) do
+    case :erlang.md5(key <> Integer.to_string(nonce)) do
+      <<0::20, _::108>> -> nonce
+      _ -> mine_advent_coin(key, 5, nonce + 1)
+    end
+  end
+
+  defp mine_advent_coin(key, 6, nonce) do
+    case :erlang.md5(key <> Integer.to_string(nonce)) do
+      <<0::24, _::104>> -> nonce
+      _ -> mine_advent_coin(key, 6, nonce + 1)
+    end
+  end
+
+  def p2 do
+    input_string()
+    |> String.trim()
+    |> mine_advent_coin(6)
+  end
+end

2015/lib/2015/5.ex

@@ -0,0 +1,29 @@
+import AOC
+
+aoc 2015, 5 do
+  @deny_list ~w(ab cd pq xy)
+
+  def p1 do
+    input_stream()
+    |> Stream.filter(&is_string_nice_p1?/1)
+    |> Enum.count()
+  end
+
+  defp is_string_nice_p1?(str) do
+    contains_at_least_three_vowels = String.match?(str, ~r/(?:[aeiou].*){3}/)
+    contains_double_letter = String.match?(str, ~r/(\w)\1/)
+    does_not_contain_denylist = not Enum.any?(@deny_list, &String.contains?(str, &1))
+
+    contains_at_least_three_vowels and contains_double_letter and does_not_contain_denylist
+  end
+
+  def p2 do
+    input_stream()
+    |> Stream.filter(&is_string_nice_p2?/1)
+    |> Enum.count()
+  end
+
+  defp is_string_nice_p2?(str) do
+    String.match?(str, ~r/(\w)(\w).*\1\2/) and String.match?(str, ~r/(\w)\w\1/)
+  end
+end

2015/lib/2015/6.ex

@@ -0,0 +1,82 @@
+import AOC
+
+aoc 2015, 6 do
+  import NimbleParsec
+
+  defparsec(
+    :coord,
+    integer(min: 1)
+    |> ignore(string(","))
+    |> integer(min: 1)
+    |> label("coordinate pair")
+  )
+
+  defparsec(
+    :command,
+    choice([
+      string("turn on"),
+      string("turn off"),
+      string("toggle")
+    ])
+    |> ignore(string(" "))
+    |> parsec(:coord)
+    |> ignore(string(" through "))
+    |> parsec(:coord)
+  )
+
+  def parse_command(line) do
+    command(line)
+    |> then(fn {:ok, v, _, _, _, _} -> v end)
+    |> then(fn
+      ["turn on", x1, y1, x2, y2] -> {:turn_on, {x1, y1}, {x2, y2}}
+      ["turn off", x1, y1, x2, y2] -> {:turn_off, {x1, y1}, {x2, y2}}
+      ["toggle", x1, y1, x2, y2] -> {:toggle, {x1, y1}, {x2, y2}}
+    end)
+  end
+
+  def command_stream(), do: input_stream() |> Stream.map(&parse_command/1)
+
+  def p1 do
+    lights = for x <- 0..999, y <- 0..999, into: %{}, do: {{x, y}, 0}
+
+    command_stream()
+    |> Enum.reduce(lights, fn
+      {:turn_on, from, to}, lights ->
+        set_range(lights, from, to, 1)
+
+      {:turn_off, from, to}, lights ->
+        set_range(lights, from, to, 0)
+
+      {:toggle, from, to}, lights ->
+        update_range(lights, from, to, fn
+          0 -> 1
+          1 -> 0
+        end)
+    end)
+    |> Map.values()
+    |> Enum.sum()
+  end
+
+  def p2 do
+    lights = for x <- 0..999, y <- 0..999, into: %{}, do: {{x, y}, 0}
+
+    command_stream()
+    |> Enum.reduce(lights, fn
+      {:turn_on, from, to}, lights -> update_range(lights, from, to, &(&1 + 1))
+      {:turn_off, from, to}, lights -> update_range(lights, from, to, &max(0, &1 - 1))
+      {:toggle, from, to}, lights -> update_range(lights, from, to, &(&1 + 2))
+    end)
+    |> Map.values()
+    |> Enum.sum()
+  end
+
+  def set_range(map, from, to, value), do: update_range(map, from, to, always(value))
+
+  def update_range(map, {x1, y1}, {x2, y2}, fun) do
+    for x <- x1..x2, y <- y1..y2, reduce: map do
+      map -> Map.update!(map, {x, y}, fun)
+    end
+  end
+
+  def always(v), do: fn _ -> v end
+end

2015/lib/2015/7.ex

@@ -0,0 +1,14 @@
+import AOC
+
+aoc 2015, 7 do
+  import NimbleParsec
+
+  def parse_inst(line) do
+  end
+
+  def p1 do
+  end
+
+  def p2 do
+  end
+end

2015/lib/advent_of_code2015.ex

@@ -0,0 +1,18 @@
+defmodule AdventOfCode2015 do
+  @moduledoc """
+  Documentation for `AdventOfCode2015`.
+  """
+
+  @doc """
+  Hello world.
+
+  ## Examples
+
+      iex> AdventOfCode2015.hello()
+      :world
+
+  """
+  def hello do
+    :world
+  end
+end

2015/mix.exs

@@ -0,0 +1,30 @@
+defmodule AdventOfCode2015.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :advent_of_code_2015,
+      version: "0.1.0",
+      elixir: "~> 1.12",
+      start_permanent: Mix.env() == :prod,
+      deps: deps()
+    ]
+  end
+
+  # Run "mix help compile.app" to learn about applications.
+  def application do
+    [
+      extra_applications: [:logger]
+    ]
+  end
+
+  # Run "mix help deps" to learn about dependencies.
+  defp deps do
+    [
+      {:advent_of_code_utils, "~> 1.0"},
+      {:exla, "~> 0.1.0-dev", github: "elixir-nx/nx", sparse: "exla"},
+      {:nimble_parsec, "~> 1.0"},
+      {:nx, "~> 0.1.0-dev", github: "elixir-nx/nx", sparse: "nx", override: true}
+    ]
+  end
+end

2015/mix.lock

@@ -0,0 +1,8 @@
+%{
+  "advent_of_code_utils": {:hex, :advent_of_code_utils, "1.0.0", "e9ce8be22988e095991168e9d2dde802afc213aaae64491e9fde84dd877db41c", [:mix], [], "hexpm", "1fa5217ccb95a38ce2312dd7ea6057b0d0002a3eba7490feab704df4b8a94038"},
+  "elixir_make": {:hex, :elixir_make, "0.6.3", "bc07d53221216838d79e03a8019d0839786703129599e9619f4ab74c8c096eac", [:mix], [], "hexpm", "f5cbd651c5678bcaabdbb7857658ee106b12509cd976c2c2fca99688e1daf716"},
+  "exla": {:git, "https://github.com/elixir-nx/nx.git", "e23a678bf0ebcbbafe03f1b5ed78623f052ad486", [sparse: "exla"]},
+  "nimble_parsec": {:hex, :nimble_parsec, "1.2.0", "b44d75e2a6542dcb6acf5d71c32c74ca88960421b6874777f79153bbbbd7dccc", [:mix], [], "hexpm", "52b2871a7515a5ac49b00f214e4165a40724cf99798d8e4a65e4fd64ebd002c1"},
+  "nx": {:git, "https://github.com/elixir-nx/nx.git", "e23a678bf0ebcbbafe03f1b5ed78623f052ad486", [sparse: "nx"]},
+  "xla": {:hex, :xla, "0.2.0", "689887888afb22587168d461f0e9ff83d7b06040273ea7082dbf9ff7eca33dcc", [:make, :mix], [{:elixir_make, "~> 0.4", [hex: :elixir_make, repo: "hexpm", optional: false]}], "hexpm", "a2e7b81413db49a159eabfb12dbd784a7c04b5c68c7b4057238d5ec9b110f2ec"},
+}

2015/test/advent_of_code2015_test.exs

@@ -0,0 +1,8 @@
+defmodule AdventOfCode2015Test do
+  use ExUnit.Case
+  doctest AdventOfCode2015
+
+  test "greets the world" do
+    assert AdventOfCode2015.hello() == :world
+  end
+end

2015/test/test_helper.exs

@@ -0,0 +1 @@
+ExUnit.start()