Alright! We’re halfway through! The puzzle today is easier than the last, as a “monday” puzzle would, but it is fun nontheless. The puzzle format break out from the tradition of “compute in this method and return this number.” To solve for the puzzle today, you actually have to visualize to see the output.
Part 1
Show challenge - day 13, part 1
You reach another volcanically active part of the cave. It would be nice if you could do some kind of thermal imaging so you could tell ahead of time which caves are too hot to safely enter.
Fortunately, the submarine seems to be equipped with a thermal camera! When you activate it, you are greeted with:
Congratulations on your purchase! To activate this infrared thermal imaging camera system, please enter the code found on page 1 of the manual.
Apparently, the Elves have never used this feature. To your surprise, you manage to find the manual; as you go to open it, page 1 falls out. It’s a large sheet of transparent paper! The transparent paper is marked with random dots and includes instructions on how to fold it up (your puzzle input). For example:
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
The first section is a list of dots on the transparent paper.
0,0 represents the top-left coordinate. The first value, x, increases to the right. The second value, y, increases downward. So, the coordinate 3,0 is to the right of 0,0, and the coordinate 0,7 is below 0,0.
The coordinates in this example form the following pattern, where # is a dot on the paper and . is an empty, unmarked position:
...#..#..#.
....#......
...........
#..........
...#....#.#
...........
...........
...........
...........
...........
.#....#.##.
....#......
......#...#
#..........
#.#........
Then, there is a list of fold instructions.
Each instruction indicates a line on the transparent paper and wants you to fold the paper up (for horizontal y = ... lines) or left (for vertical x = ... lines).
In this example, the first fold instruction is fold along y=7, which designates the line formed by all of the positions where y is 7 (marked here with -):
...#..#..#.
....#......
...........
#..........
...#....#.#
...........
...........
-----------
...........
...........
.#....#.##.
....#......
......#...#
#..........
Because this is a horizontal line, fold the bottom half up. Some of the dots might end up overlapping after the fold is complete, but dots will never appear exactly on a fold line. The result of doing this fold looks like this:
#.##..#..#.
#...#......
......#...#
#...#......
.#.#..#.###
...........
...........
Now, only 17 dots are visible.
Notice, for example, the two dots in the bottom left corner before the transparent paper is folded; after the fold is complete, those dots appear in the top left corner (at 0,0 and 0,1).
Because the paper is transparent, the dot just below them in the result (at 0,3) remains visible, as it can be seen through the transparent paper.
Also notice that some dots can end up overlapping; in this case, the dots merge together and become a single dot.
The second fold instruction is fold along x=5, which indicates this line:
#.##.|#..#.
#...#|.....
.....|#...#
#...#|.....
.#.#.|#.###
.....|.....
.....|.....
Because this is a vertical line, fold left:
#####
#...#
#...#
#...#
#####
.....
.....
The instructions made a square!
The transparent paper is pretty big, so for now, focus on just completing the first fold.
After the first fold in the example above, 17 dots are visible - dots that end up overlapping after the fold is completed count as a single dot.
How many dots are visible after completing just the first fold instruction on your transparent paper?
Here’s the provided input. It’s quite long so don’t try to scroll through:
Show input - day 13
94,530
698,875
221,18
1232,443
689,509
1153,225
239,16
1265,275
589,264
594,766
882,159
1245,435
6,686
383,488
497,535
601,353
326,330
1277,509
773,239
331,567
174,43
1047,551
771,358
716,871
1215,346
228,357
703,647
1272,299
363,668
967,248
1145,490
160,194
912,410
227,623
1041,402
811,257
50,505
67,772
211,275
751,38
1078,311
552,590
1280,389
1031,91
102,654
361,590
50,241
1225,445
658,773
1101,844
785,89
244,294
984,564
703,592
430,493
703,131
214,345
922,247
706,35
515,410
724,560
1113,325
735,70
1195,747
244,136
572,92
1285,889
813,227
1245,591
423,38
962,708
489,42
865,687
798,603
271,777
1299,854
55,117
885,182
952,680
1126,99
129,275
69,770
1305,1
65,683
880,204
224,142
1235,151
174,345
1285,827
1263,112
1215,548
50,884
556,805
288,147
167,259
47,434
417,796
609,54
147,79
848,385
1305,451
795,585
569,472
197,649
837,371
306,862
924,863
539,171
1220,414
909,749
1041,191
666,28
716,128
1091,613
927,614
686,120
1200,98
1255,466
161,294
952,438
43,651
445,739
1235,781
217,501
42,371
33,304
386,863
783,575
999,304
412,527
239,591
303,624
622,794
186,572
785,469
1213,712
311,696
459,240
922,43
694,523
107,820
1181,619
1007,624
454,847
607,434
1225,893
393,795
1113,693
430,752
388,549
433,402
115,723
522,376
713,624
801,819
884,145
60,871
823,259
1263,24
124,875
601,725
459,654
1190,19
1113,309
1298,798
1086,817
1231,294
919,551
151,700
539,536
574,449
544,546
604,35
569,422
25,148
1230,781
587,351
915,95
1056,851
1170,630
915,150
1278,100
552,142
132,518
129,537
1265,726
410,316
1285,372
763,57
11,563
1076,348
82,802
977,256
1260,35
470,795
1039,366
388,345
1225,870
1208,240
1016,346
244,758
254,851
244,86
1310,493
567,71
11,115
1230,449
711,565
157,225
856,847
350,583
694,595
1267,651
1115,128
1110,47
1233,333
1208,654
27,333
845,665
539,397
445,687
1041,703
800,607
960,535
288,803
165,294
537,168
186,322
686,680
1099,723
607,302
1101,626
375,593
525,201
609,51
373,207
20,829
157,618
11,854
139,36
1009,596
657,647
410,578
301,521
348,186
69,796
1086,204
771,210
515,833
924,31
1288,359
647,301
949,749
527,127
1207,280
689,23
629,827
661,767
1034,483
785,201
500,851
853,721
1183,220
735,824
437,841
959,624
601,801
1153,669
224,369
741,445
457,721
385,492
1195,397
828,267
1039,152
415,814
785,581
209,50
1153,618
25,827
821,42
271,614
721,264
1038,534
900,561
726,715
1017,593
795,36
197,693
758,240
701,627
557,438
856,47
497,359
426,145
594,128
883,159
1113,203
604,211
925,639
927,329
57,165
807,331
258,535
905,2
745,383
629,789
411,712
348,513
145,159
80,449
412,367
922,269
232,306
415,815
1014,774
382,534
950,324
803,752
243,182
895,416
395,346
246,70
657,695
539,312
455,660
261,815
386,31
47,460
816,194
214,212
599,117
1186,875
621,509
845,682
683,781
415,192
244,600
157,807
599,565
909,348
788,341
102,401
242,199
718,623
962,186
77,674
279,91
884,537
537,339
430,401
547,728
706,57
899,712
233,210
1054,133
195,94
234,800
679,645
845,821
545,877
597,624
560,87
768,72
269,255
723,351
383,329
1208,80
233,236
15,847
704,136
949,593
1243,122
321,451
314,768
1245,640
1243,827
1288,535
1071,430
612,875
1220,480
648,208
758,752
979,623
1071,591
542,212
455,220
89,511
898,367
415,863
686,57
127,212
358,241
937,504
1113,17
851,240
343,752
575,70
366,539
12,798
229,357
694,299
698,75
1260,505
25,522
1089,453
358,438
1150,194
1184,847
801,75
851,128
80,781
1099,275
1179,128
582,704
45,331
38,299
1073,369
1242,670
925,492
259,772
221,5
209,319
1245,683
1179,318
1250,542
261,795
1158,82
161,714
5,1
1207,614
783,569
1205,624
688,794
890,240
375,472
502,68
989,575
428,159
195,766
689,749
547,57
299,113
36,271
1068,3
1263,220
888,588
502,569
917,99
900,578
47,220
1081,357
870,549
237,749
430,849
1195,723
900,310
793,560
741,449
831,476
433,492
1073,322
1086,369
959,270
334,686
1228,362
90,414
507,367
412,871
851,352
70,627
33,509
152,826
539,582
755,175
405,450
507,424
528,47
1165,159
1032,360
1250,871
987,719
932,483
821,600
566,777
724,476
1004,708
937,275
1086,33
1073,145
865,207
1081,327
358,689
525,469
261,192
927,186
0,401
724,334
127,767
917,254
709,93
567,255
361,369
1171,36
527,276
527,679
566,49
726,267
835,200
373,619
771,684
445,851
825,618
465,821
358,217
1263,560
406,115
1200,460
1082,593
485,186
923,485
343,740
426,357
570,891
274,236
355,113
165,376
1081,771
291,226
877,889
917,547
480,569
73,546
782,847
1195,312
1295,847
290,847
55,466
808,549
209,626
870,212
433,876
267,409
1183,773
1226,199
22,359
621,357
229,119
913,348
160,700
206,539
534,19
1041,553
1159,3
979,775
291,312
1113,245
417,301
282,551
1203,389
1029,267
465,229
1006,135
1166,607
1195,110
880,401
570,443
733,333
375,723
137,560
1173,560
303,49
930,210
681,446
209,844
25,746
1086,304
1153,807
1260,389
296,205
821,516
935,723
1082,145
773,339
32,346
1263,782
448,803
853,247
107,389
68,476
420,546
793,334
771,397
694,803
547,389
977,319
1039,565
561,236
559,184
750,87
1145,294
490,621
667,563
661,443
527,220
862,467
1022,91
197,201
171,705
1155,637
704,758
50,35
195,318
882,735
1242,476
662,208
855,212
92,124
248,442
745,572
858,691
1086,861
701,838
348,750
50,145
877,453
102,814
50,859
1241,796
661,127
271,117
68,535
231,548
293,752
440,613
604,859
929,568
256,133
587,515
663,301
920,495
967,198
228,593
691,836
1082,357
835,246
1129,147
768,568
808,180
1203,148
1310,655
258,588
837,819
224,33
490,273
880,690
715,840
401,546
1069,63
542,568
1285,334
880,493
1066,86
1096,345
736,449
258,359
1300,361
724,418
1227,264
609,715
152,549
713,105
373,838
75,113
475,246
1200,796
649,443
552,752
821,294
32,324
766,546
708,658
744,845
272,534
488,638
795,484
53,1
219,515
1113,761
733,561
853,581
949,200
60,493
1228,84
5,893
185,633
209,268
877,18
840,99
331,775
952,653
197,17
480,325
171,854
102,449
937,723
783,851
711,728
209,575
517,334
1029,627
1081,119
504,894
427,159
895,16
181,747
512,603
701,54
266,1
338,740
607,197
155,637
914,588
324,213
55,329
1235,743
169,276
197,877
1104,19
179,470
243,712
602,658
900,92
393,99
410,92
1039,280
1014,680
994,861
927,280
253,301
1233,561
1044,549
485,260
589,470
102,80
507,143
457,581
706,837
509,159
1004,144
415,366
214,281
237,572
112,774
920,399
766,348
324,325
1260,859
607,112
900,802
72,179
830,569
1161,710
373,396
269,639
922,177
714,843
1135,292
333,506
90,480
67,827
1077,210
596,843
443,275
820,273
873,841
1014,438
306,144
479,602
987,327
703,302
552,829
232,311
1257,353
393,264
990,208
12,96
979,719
497,667
1007,270
353,827
947,668
271,708
221,453
102,445
221,402
393,254
1068,199
253,266
231,856
1113,585
731,319
518,584
301,821
923,877
147,815
701,267
1108,203
329,292
425,323
986,213
817,628
1183,682
72,715
256,410
475,200
709,801
564,414
120,19
459,352
949,145
390,399
1044,585
242,695
445,50
1046,399
1044,43
840,200
206,19
82,810
67,351
144,287
304,135
127,575
1126,795
566,397
68,670
624,241
522,518
1260,145
1031,472
244,578
758,829
223,17
321,388
624,568
1086,466
1235,878
793,441
165,742
586,672
564,480
197,203
294,548
1268,371
880,1
629,446
875,67
1145,518
415,519
937,838
1171,858
425,771
242,891
721,303
731,255
82,767
934,310
383,614
994,476
1158,569
22,535
792,534
1115,542
1208,304
1044,814
959,497
738,308
855,220
1043,409
239,303
47,91
611,203
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
Here’s the solution to part 1:
using Pipe: @pipe
points, instructions = split(strip(input), "\n\n")
points = @pipe split.(split(points, "\n"), ",") .|> parse.(Int, _)
instructions = @pipe split(instructions, "\n") .|> (_[12:12], parse(Int, _[14:end]))
mirror(vec, pos) = [val .> pos ? .- val .+ (pos*2) : val for val in vec]
function fold(direction, position, points)
direction == "x" ? dim = 1 : dim = 2
mirrored = mirror(getindex.(points, dim), position)
out = copy(points)
for i in 1:length(out)
out[i][dim] = mirrored[i]
end
return out
end
points = fold(instructions[1]..., points)
points |> unique |> length |> print
Part 2
Show challenge - day 13, part 2
Finish folding the transparent paper according to the instructions. The manual says the code is always eight capital letters.
What code do you use to activate the infrared thermal imaging camera system?
Here’s the solution to part 2:
using Pipe: @pipe
using UnicodePlots
points, instructions = split(strip(input), "\n\n")
points = @pipe split.(split(points, "\n"), ",") .|> parse.(Int, _)
instructions = @pipe split(instructions, "\n") .|> (_[12:12], parse(Int, _[14:end]))
mirror(vec, pos) = [val .> pos ? .- val .+ (pos*2) : val for val in vec]
function fold(direction, position, points)
direction == "x" ? dim = 1 : dim = 2
mirrored = mirror(getindex.(points, dim), position)
out = copy(points)
for i in 1:length(out)
out[i][dim] = mirrored[i]
end
return out
end
for instruction in instructions
points = fold(instruction..., points)
end
frame = @pipe points |> hcat(_...) |>
maximum(_; dims=2) |> .+(_, 1) |> zeros(_...)
for point in points
frame[(point .+ 1)...] = 1
end
heatmap(reverse(frame', dims = 1)) |> display
For me, the lastest command returned this:
