43 lines
1.5 KiB
Text
43 lines
1.5 KiB
Text
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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](https://en.wikipedia.org/wiki/Chiton), and it would be best not to 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 input). For example:
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```
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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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```
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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 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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```
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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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```
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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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To begin, [get your puzzle input](15/input).
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Answer:
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