199 lines
9.0 KiB
Plaintext
199 lines
9.0 KiB
Plaintext
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# Advent of Code
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--- Day 15: Chiton ---
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You've almost reached the exit of the cave, but the walls are getting closer together. Your submarine can barely still fit, though; the main problem is that the walls of the cave are covered in chitons, and it would be best not to
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bump any of them.
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The cavern is large, but has a very low ceiling, restricting your motion to two dimensions. The shape of the cavern resembles a square; a quick scan of chiton density produces a map of risk level throughout the cave (your puzzle
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input). For example:
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1163751742
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1381373672
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2136511328
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3694931569
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7463417111
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1319128137
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1359912421
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3125421639
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1293138521
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2311944581
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You start in the top left position, your destination is the bottom right position, and you cannot move diagonally. The number at each position is its risk level; to determine the total risk of an entire path, add up the risk levels
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of each position you enter (that is, don't count the risk level of your starting position unless you enter it; leaving it adds no risk to your total).
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Your goal is to find a path with the lowest total risk. In this example, a path with the lowest total risk is highlighted here:
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1163751742
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1381373672
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2136511328
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3694931569
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7463417111
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1319128137
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1359912421
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3125421639
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1293138521
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2311944581
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The total risk of this path is 40 (the starting position is never entered, so its risk is not counted).
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What is the lowest total risk of any path from the top left to the bottom right?
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Your puzzle answer was 366.
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--- Part Two ---
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Now that you know how to find low-risk paths in the cave, you can try to find your way out.
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The entire cave is actually five times larger in both dimensions than you thought; the area you originally scanned is just one tile in a 5x5 tile area that forms the full map. Your original map tile repeats to the right and
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downward; each time the tile repeats to the right or downward, all of its risk levels are 1 higher than the tile immediately up or left of it. However, risk levels above 9 wrap back around to 1. So, if your original map had some
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position with a risk level of 8, then that same position on each of the 25 total tiles would be as follows:
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8 9 1 2 3
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9 1 2 3 4
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1 2 3 4 5
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2 3 4 5 6
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3 4 5 6 7
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Each single digit above corresponds to the example position with a value of 8 on the top-left tile. Because the full map is actually five times larger in both dimensions, that position appears a total of 25 times, once in each
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duplicated tile, with the values shown above.
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Here is the full five-times-as-large version of the first example above, with the original map in the top left corner highlighted:
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11637517422274862853338597396444961841755517295286
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13813736722492484783351359589446246169155735727126
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21365113283247622439435873354154698446526571955763
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36949315694715142671582625378269373648937148475914
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74634171118574528222968563933317967414442817852555
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13191281372421239248353234135946434524615754563572
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13599124212461123532357223464346833457545794456865
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31254216394236532741534764385264587549637569865174
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12931385212314249632342535174345364628545647573965
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23119445813422155692453326671356443778246755488935
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22748628533385973964449618417555172952866628316397
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24924847833513595894462461691557357271266846838237
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32476224394358733541546984465265719557637682166874
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47151426715826253782693736489371484759148259586125
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85745282229685639333179674144428178525553928963666
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24212392483532341359464345246157545635726865674683
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24611235323572234643468334575457944568656815567976
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42365327415347643852645875496375698651748671976285
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23142496323425351743453646285456475739656758684176
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34221556924533266713564437782467554889357866599146
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33859739644496184175551729528666283163977739427418
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35135958944624616915573572712668468382377957949348
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43587335415469844652657195576376821668748793277985
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58262537826937364893714847591482595861259361697236
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96856393331796741444281785255539289636664139174777
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35323413594643452461575456357268656746837976785794
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35722346434683345754579445686568155679767926678187
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53476438526458754963756986517486719762859782187396
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34253517434536462854564757396567586841767869795287
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45332667135644377824675548893578665991468977611257
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44961841755517295286662831639777394274188841538529
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46246169155735727126684683823779579493488168151459
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54698446526571955763768216687487932779859814388196
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69373648937148475914825958612593616972361472718347
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17967414442817852555392896366641391747775241285888
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46434524615754563572686567468379767857948187896815
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46833457545794456865681556797679266781878137789298
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64587549637569865174867197628597821873961893298417
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45364628545647573965675868417678697952878971816398
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56443778246755488935786659914689776112579188722368
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55172952866628316397773942741888415385299952649631
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57357271266846838237795794934881681514599279262561
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65719557637682166874879327798598143881961925499217
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71484759148259586125936169723614727183472583829458
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28178525553928963666413917477752412858886352396999
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57545635726865674683797678579481878968159298917926
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57944568656815567976792667818781377892989248891319
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75698651748671976285978218739618932984172914319528
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56475739656758684176786979528789718163989182927419
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67554889357866599146897761125791887223681299833479
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Equipped with the full map, you can now find a path from the top left corner to the bottom right corner with the lowest total risk:
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11637517422274862853338597396444961841755517295286
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13813736722492484783351359589446246169155735727126
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21365113283247622439435873354154698446526571955763
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36949315694715142671582625378269373648937148475914
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74634171118574528222968563933317967414442817852555
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13191281372421239248353234135946434524615754563572
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13599124212461123532357223464346833457545794456865
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31254216394236532741534764385264587549637569865174
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12931385212314249632342535174345364628545647573965
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23119445813422155692453326671356443778246755488935
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22748628533385973964449618417555172952866628316397
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24924847833513595894462461691557357271266846838237
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32476224394358733541546984465265719557637682166874
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47151426715826253782693736489371484759148259586125
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85745282229685639333179674144428178525553928963666
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24212392483532341359464345246157545635726865674683
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24611235323572234643468334575457944568656815567976
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42365327415347643852645875496375698651748671976285
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23142496323425351743453646285456475739656758684176
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34221556924533266713564437782467554889357866599146
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33859739644496184175551729528666283163977739427418
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35135958944624616915573572712668468382377957949348
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43587335415469844652657195576376821668748793277985
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58262537826937364893714847591482595861259361697236
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96856393331796741444281785255539289636664139174777
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35323413594643452461575456357268656746837976785794
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35722346434683345754579445686568155679767926678187
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53476438526458754963756986517486719762859782187396
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34253517434536462854564757396567586841767869795287
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45332667135644377824675548893578665991468977611257
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44961841755517295286662831639777394274188841538529
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46246169155735727126684683823779579493488168151459
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54698446526571955763768216687487932779859814388196
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69373648937148475914825958612593616972361472718347
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17967414442817852555392896366641391747775241285888
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46434524615754563572686567468379767857948187896815
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46833457545794456865681556797679266781878137789298
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64587549637569865174867197628597821873961893298417
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45364628545647573965675868417678697952878971816398
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56443778246755488935786659914689776112579188722368
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55172952866628316397773942741888415385299952649631
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57357271266846838237795794934881681514599279262561
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65719557637682166874879327798598143881961925499217
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71484759148259586125936169723614727183472583829458
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28178525553928963666413917477752412858886352396999
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57545635726865674683797678579481878968159298917926
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57944568656815567976792667818781377892989248891319
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75698651748671976285978218739618932984172914319528
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56475739656758684176786979528789718163989182927419
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67554889357866599146897761125791887223681299833479
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The total risk of this path is 315 (the starting position is still never entered, so its risk is not counted).
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Using the full map, what is the lowest total risk of any path from the top left to the bottom right?
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Your puzzle answer was 2829.
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Both parts of this puzzle are complete! They provide two gold stars: **
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At this point, all that is left is for you to admire your Advent calendar.
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If you still want to see it, you can get your puzzle input.
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References
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Visible links
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. https://adventofcode.com/
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. https://adventofcode.com/2021/about
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. https://adventofcode.com/2021/events
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. https://adventofcode.com/2021/settings
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. https://adventofcode.com/2021/auth/logout
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. Advent of Code Supporter
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https://adventofcode.com/2021/support
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. https://adventofcode.com/2021
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. https://adventofcode.com/2021
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. https://adventofcode.com/2021/support
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. https://adventofcode.com/2021/sponsors
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. https://adventofcode.com/2021/leaderboard
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. https://adventofcode.com/2021/stats
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. https://adventofcode.com/2021/sponsors
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. https://en.wikipedia.org/wiki/Chiton
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. https://adventofcode.com/2021
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. https://adventofcode.com/2021/day/15/input
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