commit ac59777db333e40d23938c9148d5f0953515dcbc
parent e38ebb7fcfc7a00fba183c1d6b178a0da0bc1fc6
Author: Eamon Caddigan <eamon.caddigan@gmail.com>
Date: Fri, 9 Dec 2022 14:43:26 -0800
Solution to day 9, part 1.
Diffstat:
| A | src/day_9.jl | | | 77 | +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
1 file changed, 77 insertions(+), 0 deletions(-)
diff --git a/src/day_9.jl b/src/day_9.jl
@@ -0,0 +1,77 @@
+#!/usr/bin/env julia
+# https://adventofcode.com/2022/day/9
+using AdventOfCode
+
+example = readlines(IOBuffer("""
+ R 4
+ U 4
+ L 3
+ D 1
+ R 4
+ D 1
+ L 5
+ R 2"""))
+input = readlines("data/day_9.txt")
+
+function increment_head_tail(head_position::Tuple{Int,Int},
+ tail_position::Tuple{Int,Int},
+ direction::Char)
+ if direction == 'L'
+ if head_position[1] - tail_position[1] < 0
+ tail_position = head_position
+ end
+ head_position = (head_position[1] - 1, head_position[2])
+ elseif direction == 'R'
+ if head_position[1] - tail_position[1] > 0
+ tail_position = head_position
+ end
+ head_position = (head_position[1] + 1, head_position[2])
+ elseif direction == 'D'
+ if head_position[2] - tail_position[2] < 0
+ tail_position = head_position
+ end
+ head_position = (head_position[1], head_position[2] - 1)
+ elseif direction == 'U'
+ if head_position[2] - tail_position[2] > 0
+ tail_position = head_position
+ end
+ head_position = (head_position[1], head_position[2] + 1)
+ else
+ error("invalid direction")
+ end
+
+ (head_position, tail_position)
+end
+
+function move_head_tail(instructions)
+ head_position, tail_position = ((0,0), (0,0))
+ tail_visits = Set{Tuple{Int,Int}}()
+ push!(tail_visits, tail_position)
+
+ for instruction = instructions
+ direction = instruction[1]
+ steps = parse(Int, instruction[3:end])
+ for _ = 1:steps
+ head_position, tail_position = increment_head_tail(
+ head_position,
+ tail_position,
+ direction
+ )
+ push!(tail_visits, tail_position)
+ end
+ end
+
+ tail_visits
+end
+
+function part_1(input)
+ length(move_head_tail(input))
+end
+@assert part_1(example) == 13
+@info part_1(input)
+
+function part_2(input)
+ nothing
+end
+@assert part_2(example) == nothing
+@info part_2(input)
