2022 day 9, Bash part 1

2022/day09/README.org

@@ -283,3 +283,463 @@ So, there are =13= positions the tail visited at least once.
 
 Simulate your complete hypothetical series of motions. /How many
 positions does the tail of the rope visit at least once?/
+
+Your puzzle answer was =5619=.
+
+The first half of this puzzle is complete! It provides one gold star: *
+
+** --- Part Two ---
+A rope snaps! Suddenly, the river is getting a lot closer than you
+remember. The bridge is still there, but some of the ropes that broke
+are now whipping toward you as you fall through the air!
+
+The ropes are moving too quickly to grab; you only have a few seconds to
+choose how to arch your body to avoid being hit. Fortunately, your
+simulation can be extended to support longer ropes.
+
+Rather than two knots, you now must simulate a rope consisting of /ten/
+knots. One knot is still the head of the rope and moves according to the
+series of motions. Each knot further down the rope follows the knot in
+front of it using the same rules as before.
+
+Using the same series of motions as the above example, but with the
+knots marked =H=, =1=, =2=, ..., =9=, the motions now occur as follows:
+
+#+begin_example
+== Initial State ==
+
+......
+......
+......
+......
+H.....  (H covers 1, 2, 3, 4, 5, 6, 7, 8, 9, s)
+
+== R 4 ==
+
+......
+......
+......
+......
+1H....  (1 covers 2, 3, 4, 5, 6, 7, 8, 9, s)
+
+......
+......
+......
+......
+21H...  (2 covers 3, 4, 5, 6, 7, 8, 9, s)
+
+......
+......
+......
+......
+321H..  (3 covers 4, 5, 6, 7, 8, 9, s)
+
+......
+......
+......
+......
+4321H.  (4 covers 5, 6, 7, 8, 9, s)
+
+== U 4 ==
+
+......
+......
+......
+....H.
+4321..  (4 covers 5, 6, 7, 8, 9, s)
+
+......
+......
+....H.
+.4321.
+5.....  (5 covers 6, 7, 8, 9, s)
+
+......
+....H.
+....1.
+.432..
+5.....  (5 covers 6, 7, 8, 9, s)
+
+....H.
+....1.
+..432.
+.5....
+6.....  (6 covers 7, 8, 9, s)
+
+== L 3 ==
+
+...H..
+....1.
+..432.
+.5....
+6.....  (6 covers 7, 8, 9, s)
+
+..H1..
+...2..
+..43..
+.5....
+6.....  (6 covers 7, 8, 9, s)
+
+.H1...
+...2..
+..43..
+.5....
+6.....  (6 covers 7, 8, 9, s)
+
+== D 1 ==
+
+..1...
+.H.2..
+..43..
+.5....
+6.....  (6 covers 7, 8, 9, s)
+
+== R 4 ==
+
+..1...
+..H2..
+..43..
+.5....
+6.....  (6 covers 7, 8, 9, s)
+
+..1...
+...H..  (H covers 2)
+..43..
+.5....
+6.....  (6 covers 7, 8, 9, s)
+
+......
+...1H.  (1 covers 2)
+..43..
+.5....
+6.....  (6 covers 7, 8, 9, s)
+
+......
+...21H
+..43..
+.5....
+6.....  (6 covers 7, 8, 9, s)
+
+== D 1 ==
+
+......
+...21.
+..43.H
+.5....
+6.....  (6 covers 7, 8, 9, s)
+
+== L 5 ==
+
+......
+...21.
+..43H.
+.5....
+6.....  (6 covers 7, 8, 9, s)
+
+......
+...21.
+..4H..  (H covers 3)
+.5....
+6.....  (6 covers 7, 8, 9, s)
+
+......
+...2..
+..H1..  (H covers 4; 1 covers 3)
+.5....
+6.....  (6 covers 7, 8, 9, s)
+
+......
+...2..
+.H13..  (1 covers 4)
+.5....
+6.....  (6 covers 7, 8, 9, s)
+
+......
+......
+H123..  (2 covers 4)
+.5....
+6.....  (6 covers 7, 8, 9, s)
+
+== R 2 ==
+
+......
+......
+.H23..  (H covers 1; 2 covers 4)
+.5....
+6.....  (6 covers 7, 8, 9, s)
+
+......
+......
+.1H3..  (H covers 2, 4)
+.5....
+6.....  (6 covers 7, 8, 9, s)
+#+end_example
+
+Now, you need to keep track of the positions the new tail, =9=, visits.
+In this example, the tail never moves, and so it only visits =1=
+position. However, /be careful/: more types of motion are possible than
+before, so you might want to visually compare your simulated rope to the
+one above.
+
+Here's a larger example:
+
+#+begin_example
+R 5
+U 8
+L 8
+D 3
+R 17
+D 10
+L 25
+U 20
+#+end_example
+
+These motions occur as follows (individual steps are not shown):
+
+#+begin_example
+== Initial State ==
+
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+...........H..............  (H covers 1, 2, 3, 4, 5, 6, 7, 8, 9, s)
+..........................
+..........................
+..........................
+..........................
+..........................
+
+== R 5 ==
+
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+...........54321H.........  (5 covers 6, 7, 8, 9, s)
+..........................
+..........................
+..........................
+..........................
+..........................
+
+== U 8 ==
+
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+................H.........
+................1.........
+................2.........
+................3.........
+...............54.........
+..............6...........
+.............7............
+............8.............
+...........9..............  (9 covers s)
+..........................
+..........................
+..........................
+..........................
+..........................
+
+== L 8 ==
+
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+........H1234.............
+............5.............
+............6.............
+............7.............
+............8.............
+............9.............
+..........................
+..........................
+...........s..............
+..........................
+..........................
+..........................
+..........................
+..........................
+
+== D 3 ==
+
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+.........2345.............
+........1...6.............
+........H...7.............
+............8.............
+............9.............
+..........................
+..........................
+...........s..............
+..........................
+..........................
+..........................
+..........................
+..........................
+
+== R 17 ==
+
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+................987654321H
+..........................
+..........................
+..........................
+..........................
+...........s..............
+..........................
+..........................
+..........................
+..........................
+..........................
+
+== D 10 ==
+
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+...........s.........98765
+.........................4
+.........................3
+.........................2
+.........................1
+.........................H
+
+== L 25 ==
+
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+...........s..............
+..........................
+..........................
+..........................
+..........................
+H123456789................
+
+== U 20 ==
+
+H.........................
+1.........................
+2.........................
+3.........................
+4.........................
+5.........................
+6.........................
+7.........................
+8.........................
+9.........................
+..........................
+..........................
+..........................
+..........................
+..........................
+...........s..............
+..........................
+..........................
+..........................
+..........................
+..........................
+#+end_example
+
+Now, the tail (=9=) visits =36= positions (including =s=) at least once:
+
+#+begin_example
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+..........................
+#.........................
+#.............###.........
+#............#...#........
+.#..........#.....#.......
+..#..........#.....#......
+...#........#.......#.....
+....#......s.........#....
+.....#..............#.....
+......#............#......
+.......#..........#.......
+........#........#........
+.........########.........
+#+end_example
+
+Simulate your complete series of motions on a larger rope with ten
+knots. /How many positions does the tail of the rope visit at least
+once?/