Bash 2022 day 12 (parts 1 & 2), before cleaning code

2022/day12/README.org

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+** --- Day 12: Hill Climbing Algorithm ---
+You try contacting the Elves using your handheld device, but the river
+you're following must be too low to get a decent signal.
+
+You ask the device for a heightmap of the surrounding area (your puzzle
+input). The heightmap shows the local area from above broken into a
+grid; the elevation of each square of the grid is given by a single
+lowercase letter, where =a= is the lowest elevation, =b= is the
+next-lowest, and so on up to the highest elevation, =z=.
+
+Also included on the heightmap are marks for your current position (=S=)
+and the location that should get the best signal (=E=). Your current
+position (=S=) has elevation =a=, and the location that should get the
+best signal (=E=) has elevation =z=.
+
+You'd like to reach =E=, but to save energy, you should do it in /as few
+steps as possible/. During each step, you can move exactly one square
+up, down, left, or right. To avoid needing to get out your climbing
+gear, the elevation of the destination square can be /at most one
+higher/ than the elevation of your current square; that is, if your
+current elevation is =m=, you could step to elevation =n=, but not to
+elevation =o=. (This also means that the elevation of the destination
+square can be much lower than the elevation of your current square.)
+
+For example:
+
+#+begin_example
+Sabqponm
+abcryxxl
+accszExk
+acctuvwj
+abdefghi
+#+end_example
+
+Here, you start in the top-left corner; your goal is near the middle.
+You could start by moving down or right, but eventually you'll need to
+head toward the =e= at the bottom. From there, you can spiral around to
+the goal:
+
+#+begin_example
+v..v<<<<
+>v.vv<<^
+.>vv>E^^
+..v>>>^^
+..>>>>>^
+#+end_example
+
+In the above diagram, the symbols indicate whether the path exits each
+square moving up (=^=), down (=v=), left (=<=), or right (=>=). The
+location that should get the best signal is still =E=, and =.= marks
+unvisited squares.
+
+This path reaches the goal in =31= steps, the fewest possible.
+
+/What is the fewest steps required to move from your current position to
+the location that should get the best signal?/
+
+Your puzzle answer was =408=.
+
+** --- Part Two ---
+As you walk up the hill, you suspect that the Elves will want to turn
+this into a hiking trail. The beginning isn't very scenic, though;
+perhaps you can find a better starting point.
+
+To maximize exercise while hiking, the trail should start as low as
+possible: elevation =a=. The goal is still the square marked =E=.
+However, the trail should still be direct, taking the fewest steps to
+reach its goal. So, you'll need to find the shortest path from /any
+square at elevation =a=/ to the square marked =E=.
+
+Again consider the example from above:
+
+#+begin_example
+Sabqponm
+abcryxxl
+accszExk
+acctuvwj
+abdefghi
+#+end_example
+
+Now, there are six choices for starting position (five marked =a=, plus
+the square marked =S= that counts as being at elevation =a=). If you
+start at the bottom-left square, you can reach the goal most quickly:
+
+#+begin_example
+...v<<<<
+...vv<<^
+...v>E^^
+.>v>>>^^
+>^>>>>>^
+#+end_example
+
+This path reaches the goal in only =29= steps, the fewest possible.
+
+/What is the fewest steps required to move starting from any square with
+elevation =a= to the location that should get the best signal?/
+
+Your puzzle answer was =399=.
+
+Both parts of this puzzle are complete! They provide two gold stars: **