Day 13
Setup
sample = """
6,10
0,14
9,10
0,3
10,4
4,11
6,0
6,12
4,1
0,13
10,12
3,4
3,0
8,4
1,10
2,14
8,10
9,0
fold along y=7
fold along x=5
"""
input = """
1053,618
966,812
363,813
663,488
582,93
112,175
887,158
647,406
1049,281
820,632
828,429
1208,203
604,15
308,721
790,380
1007,665
60,456
460,507
192,639
45,180
192,626
627,604
458,435
683,738
1121,745
435,285
902,74
246,522
734,609
1005,861
776,610
910,491
189,745
216,362
559,427
8,465
551,229
855,163
875,609
658,203
1243,270
853,859
10,457
1012,471
587,320
666,94
1205,543
646,599
619,305
862,473
73,630
228,406
850,410
720,339
338,273
1300,273
728,93
915,432
390,599
460,484
589,522
721,837
557,298
402,497
1130,40
908,497
646,156
872,466
1161,674
470,728
751,736
549,385
633,33
1012,423
858,98
490,878
276,351
999,665
216,87
892,603
915,574
236,295
328,225
1273,287
768,127
1169,661
1079,288
902,820
768,623
797,833
524,429
1123,812
1002,721
460,36
574,746
139,588
965,143
711,810
1230,605
910,28
395,574
1176,514
438,807
932,787
489,735
144,779
940,193
867,364
920,508
438,700
7,635
284,473
98,700
443,28
1156,74
1138,429
716,75
164,508
701,714
311,437
256,432
268,642
271,733
229,540
180,376
323,134
1029,42
400,476
633,161
733,883
723,208
355,626
482,380
793,386
326,396
1186,477
1210,752
261,165
1111,778
1265,714
58,231
1302,429
95,427
974,771
378,787
246,466
187,812
892,155
378,15
472,115
1300,173
627,380
1278,571
653,735
1192,707
1066,788
445,403
440,127
431,765
599,597
98,787
920,386
559,19
189,644
291,276
346,511
291,813
785,35
1205,285
214,91
589,837
310,812
1044,19
622,771
1046,162
418,333
920,732
805,674
1289,801
547,642
1246,530
706,15
8,429
1161,628
1074,295
124,513
502,661
945,63
720,555
432,511
154,372
1169,233
555,639
160,651
377,310
75,792
448,421
850,403
366,381
90,291
180,40
489,287
1211,255
822,460
795,812
1046,508
984,498
1170,686
691,500
669,283
939,679
27,626
1289,462
723,110
146,588
651,760
634,411
492,673
341,163
435,609
1121,834
1302,795
835,213
604,799
228,854
177,668
482,429
8,123
1042,63
982,669
1283,156
622,323
10,621
638,418
373,852
244,445
515,82
472,563
966,628
774,259
391,93
604,719
633,733
735,838
458,877
214,543
638,266
982,673
879,681
490,262
900,445
572,746
964,487
261,829
408,820
805,611
129,523
443,364
118,707
1123,306
482,17
964,511
765,892
612,193
790,514
115,28
452,641
301,467
785,859
18,855
604,787
472,775
788,822
969,163
653,159
736,652
1212,194
166,236
515,677
73,182
1163,380
624,598
882,80
677,733
845,250
1081,354
134,380
556,283
524,465
59,457
236,519
1150,651
268,63
923,217
147,661
1143,760
507,787
1307,358
595,437
688,323
109,178
852,17
400,866
70,333
371,679
646,74
1158,240
388,19
815,358
1310,221
440,543
957,427
281,42
850,627
294,515
266,539
124,477
1171,217
723,494
664,156
52,585
482,465
172,148
992,17
1130,376
1138,17
336,323
1297,434
1033,534
733,746
1139,747
622,547
754,642
1044,355
711,532
684,91
212,219
236,71
1220,561
735,56
397,276
918,331
261,513
105,543
890,208
875,698
616,434
672,364
149,674
21,462
351,229
1252,7
892,333
1251,457
572,148
343,885
1260,767
164,430
922,427
753,130
1278,323
1203,226
723,574
1049,596
693,159
187,306
587,574
1215,467
360,801
1213,130
882,528
1019,276
1046,60
1163,661
242,609
1302,205
457,859
1245,221
1304,889
721,372
664,771
219,698
494,651
589,57
465,508
927,795
912,14
505,348
504,234
1213,382
462,639
460,851
545,674
360,93
77,746
427,490
1267,887
134,541
3,11
1181,523
581,630
460,450
248,285
1116,627
144,567
21,541
216,700
1158,512
124,829
944,513
574,652
460,387
199,163
678,84
72,829
67,574
135,738
363,842
519,514
1005,33
107,642
507,339
882,823
1243,208
940,682
738,746
961,661
1129,723
8,795
590,555
438,585
870,35
431,385
1173,358
277,534
1212,700
16,563
174,382
73,488
239,232
308,621
102,243
25,770
736,893
149,416
1146,669
646,820
1243,574
1123,588
356,249
392,107
956,234
527,330
330,467
947,842
987,459
664,599
477,220
1074,71
648,453
1029,337
82,596
828,514
1131,213
508,854
848,639
910,39
346,63
1000,194
3,883
1146,386
8,596
1304,5
1129,815
253,264
759,665
803,380
684,697
878,511
761,543
887,736
513,833
753,298
149,266
278,624
654,673
1047,801
323,459
341,64
592,162
460,15
1171,588
870,91
828,140
1258,540
733,148
388,355
7,406
622,541
1051,494
10,437
1161,283
1123,229
100,752
751,467
284,193
858,253
117,333
1158,437
377,86
127,703
127,731
10,273
32,291
828,380
945,287
199,283
915,880
43,7
1222,397
641,283
714,439
761,509
305,681
1118,178
980,82
1289,353
97,764
1240,113
408,18
1288,810
795,588
638,630
448,473
206,381
177,674
694,434
92,878
867,418
646,295
443,866
902,893
211,866
30,408
1064,820
672,630
187,229
1220,337
555,353
305,33
1303,635
1042,700
164,669
1165,611
6,889
806,234
944,381
1118,255
239,326
725,394
961,317
395,763
393,729
1294,530
797,681
1203,668
1091,698
1084,375
1302,596
37,287
149,628
619,788
1108,684
223,681
984,669
987,134
1171,431
761,161
902,746
477,347
1146,262
257,618
875,61
350,84
8,298
1096,543
192,66
790,541
1166,263
1002,611
1042,252
102,691
1123,431
579,792
1186,829
823,760
217,892
688,771
765,674
2,691
937,785
211,418
440,35
836,376
982,213
562,128
1094,700
1258,585
268,194
377,584
990,5
915,131
1213,512
21,161
556,194
1049,829
1192,187
902,18
257,276
937,42
513,61
194,851
1000,264
67,270
365,63
358,710
402,397
124,417
1237,264
820,508
542,127
1033,808
387,217
683,380
850,387
818,262
90,561
264,60
850,2
677,353
647,488
1104,645
761,385
440,803
1091,509
937,852
308,273
1026,421
202,641
1260,127
1079,606
171,747
853,404
55,362
790,353
284,421
1278,291
323,211
842,432
577,148
271,347
964,831
1094,428
912,432
1044,539
803,9
566,397
1260,719
400,418
289,831
1116,374
758,299
944,12
1273,735
1278,123
267,229
612,701
708,802
672,418
267,677
1161,546
1016,877
617,287
1138,148
659,760
408,74
626,803
223,213
545,892
55,810
918,563
50,767
947,529
488,236
460,520
666,437
1228,669
1111,163
803,555
139,463
10,9
1042,194
964,407
172,435
843,351
388,539
366,12
154,74
797,61
505,674
79,390
525,859
1230,746
786,205
132,822
50,175
974,323
984,396
848,252
1304,441
1250,691
530,381
552,651
960,810
1176,828
965,751
795,82
202,458
141,61
351,665
21,93
1146,878
16,630
513,661
900,876
147,787
604,879
1116,491
992,746
1116,851
276,787
984,449
733,235
402,49
227,703
721,737
883,191
1231,504
1282,803
472,331
445,340
349,661
972,416
974,604
192,642
1278,347
795,351
833,347
187,82
1047,93
1208,651
452,884
288,65
32,795
1034,614
1064,466
808,64
465,250
754,194
902,690
1091,385
366,513
855,778
1021,63
599,810
964,273
487,760
587,624
1133,674
390,732
599,362
838,563
882,814
432,164
912,462
1026,212
708,92
520,380
1260,787
875,644
189,149
408,596
726,113
259,91
1051,91
259,168
fold along x=655
fold along y=447
fold along x=327
fold along y=223
fold along x=163
fold along y=111
fold along x=81
fold along y=55
fold along x=40
fold along y=27
fold along y=13
fold along y=6
"""
Part a
defmodule Day13 do
def fold_all(paper, instructions) do
instructions
|> Enum.reduce(paper, fn {direction, number}, acc ->
acc |> fold(direction, number)
end)
end
def fold(paper, :col, col) do
paper
|> Enum.map(fn
{x, y} when y >= col -> {x, 2 * col - y}
{x, y} -> {x, y}
end)
|> Enum.uniq()
end
def fold(paper, :row, row) do
paper
|> Enum.map(fn
{x, y} when x >= row -> {2 * row - x, y}
{x, y} -> {x, y}
end)
|> Enum.uniq()
end
def dimensions(paper) do
paper
|> Enum.reduce({0, 0}, fn {x, y}, acc ->
{max(x, elem(acc, 0)), max(y, elem(acc, 1))}
end)
end
def display(paper) do
{x_max, y_max} = dimensions(paper)
for j <- 0..y_max do
for i <- 0..x_max do
if Enum.member?(paper, {i, j}) do
"# "
else
" "
end
end
|> Enum.join()
end
end
end
[paper | instructions] =
input
|> String.split("\n\n", trim: true)
paper =
paper
|> String.split(["\n", ","], trim: true)
|> Enum.map(&String.to_integer/1)
|> Enum.chunk_every(2)
|> Enum.map(&List.to_tuple/1)
instructions =
instructions
|> Enum.at(0)
|> String.split("\n", trim: true)
|> Enum.map(fn
"fold along x=" <> row -> {:row, String.to_integer(row)}
"fold along y=" <> col -> {:col, String.to_integer(col)}
end)
[{direction, number} | _other_instructions] = instructions
# Part A
paper
|> Day13.fold(direction, number)
|> Enum.count()
# Part B
paper
|> Day13.fold_all(instructions)
|> Day13.display()
