1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
|
--- Day 23: Crab Cups ---
The small crab challenges [1m[37myou[0m to a game! The crab is going to mix up some cups, and you
have to predict where they'll end up.
The cups will be arranged in a circle and labeled [1m[37mclockwise[0m (your puzzle input). For
example, if your labeling were 32415, there would be five cups in the circle; going clockwise around
the circle from the first cup, the cups would be labeled 3, 2, 4, 1, 5, and then back to 3 again.
Before the crab starts, it will designate the first cup in your list as the [1m[37mcurrent
cup[0m. The crab is then going to do [1m[37m100 moves[0m.
Each [1m[37mmove[0m, the crab does the following actions:
- The crab picks up the [1m[37mthree cups[0m that are immediately [1m[37mclockwise[0m of the
[1m[37mcurrent cup[0m. They are removed from the circle; cup spacing is adjusted as necessary to
maintain the circle.
- The crab selects a [1m[37mdestination cup[0m: the cup with a [1m[37mlabel[0m equal to the
[1m[37mcurrent cup's[0m label minus one. If this would select one of the cups that was just
picked up, the crab will keep subtracting one until it finds a cup that wasn't just picked up. If at
any point in this process the value goes below the lowest value on any cup's label, it
[1m[37mwraps around[0m to the highest value on any cup's label instead.
- The crab places the cups it just picked up so that they are [1m[37mimmediately clockwise[0m of
the destination cup. They keep the same order as when they were picked up.
- The crab selects a new [1m[37mcurrent cup[0m: the cup which is immediately clockwise of the
current cup.
For example, suppose your cup labeling were 389125467. If the crab were to do merely 10 moves, the
following changes would occur:
-- move 1 --
cups: (3) 8 9 1 2 5 4 6 7
pick up: 8, 9, 1
destination: 2
-- move 2 --
cups: 3 (2) 8 9 1 5 4 6 7
pick up: 8, 9, 1
destination: 7
-- move 3 --
cups: 3 2 (5) 4 6 7 8 9 1
pick up: 4, 6, 7
destination: 3
-- move 4 --
cups: 7 2 5 (8) 9 1 3 4 6
pick up: 9, 1, 3
destination: 7
-- move 5 --
cups: 3 2 5 8 (4) 6 7 9 1
pick up: 6, 7, 9
destination: 3
-- move 6 --
cups: 9 2 5 8 4 (1) 3 6 7
pick up: 3, 6, 7
destination: 9
-- move 7 --
cups: 7 2 5 8 4 1 (9) 3 6
pick up: 3, 6, 7
destination: 8
-- move 8 --
cups: 8 3 6 7 4 1 9 (2) 5
pick up: 5, 8, 3
destination: 1
-- move 9 --
cups: 7 4 1 5 8 3 9 2 (6)
pick up: 7, 4, 1
destination: 5
-- move 10 --
cups: (5) 7 4 1 8 3 9 2 6
pick up: 7, 4, 1
destination: 3
-- final --
cups: 5 (8) 3 7 4 1 9 2 6
In the above example, the cups' values are the labels as they appear moving clockwise around the
circle; the [1m[37mcurrent cup[0m is marked with ( ).
After the crab is done, what order will the cups be in? Starting [1m[37mafter the cup labeled
1[0m, collect the other cups' labels clockwise into a single string with no extra characters; each
number except 1 should appear exactly once. In the above example, after 10 moves, the cups clockwise
from 1 are labeled 9, 2, 6, 5, and so on, producing [1m[37m92658374[0m. If the crab were to
complete all 100 moves, the order after cup 1 would be [1m[37m67384529[0m.
Using your labeling, simulate 100 moves. [1m[37mWhat are the labels on the cups after cup 1?[0m
|
