advent_of_code_2022

commit 7539928b528e483ce9f1fa715e095d2b550d3736
parent 1452c97c449d7c66ccc7010cd3fa88efca38e1d6
Author: Eamon Caddigan <eamon.caddigan@gmail.com>
Date:   Fri,  9 Dec 2022 20:58:57 -0800

Just a bit of code cleanup.

I mean, it's still ugly. But it's a bit less ugly.

Diffstat:
M
src/day_9.jl
 | 
19
+++++++++----------

1 file changed, 9 insertions(+), 10 deletions(-)
diff --git a/src/day_9.jl b/src/day_9.jl
@@ -38,20 +38,19 @@ end
 """
 Shift the tail one step based on the difference vector
 
-The tail can move up/down, left/right, or diagonally.
+The tail can move up/down, left/right, or diagonally. It moves at most one step
+(in either or both cardinal directions).
 """
-function shift_tail(diff_vec, head_position, tail_position)
+function shift_tail(diff_vec, tail_position)
     tail_position .+ sign.(diff_vec)
 end
  
 function move_knots(instructions, num_knots=2)
     knot_positions = [(0, 0) for _ in 1:num_knots]
-    tail_visits = Set{Tuple{Int,Int}}()
-    push!(tail_visits, knot_positions[end])
+    tail_visits = Set{Tuple{Int,Int}}([knot_positions[end]])
 
     for instruction = instructions
-        steps = parse(Int, instruction[3:end])
-        for _ in 1:steps
+        for _ in 1:parse(Int, instruction[3:end]) # Number of steps
             knot_positions[1] = shift_head(
                 knot_positions[1],
                 instruction[1]
@@ -62,8 +61,8 @@ function move_knots(instructions, num_knots=2)
                                                  knot_positions[i])
                 while !aretouching
                     knot_positions[i] = shift_tail(diff_vec,
-                                                   knot_positions[i-1],
                                                    knot_positions[i])
+
                     if i == lastindex(knot_positions)
                         push!(tail_visits, knot_positions[i])
                     end
@@ -72,8 +71,8 @@ function move_knots(instructions, num_knots=2)
                                                      knot_positions[i])
                 end
             end
-        end
-    end
+        end # steps
+    end # instructions
 
     tail_visits
 end
@@ -113,9 +112,9 @@ function draw_map(tail_visits)
     println(join(reverse([join(x, "") for x in eachrow(tailmap)]), "\n"))
 end
 
-draw_map(move_knots(example2, 10))
 function part_2(input)
     length(move_knots(input, 10))
 end
 @assert part_2(example2) == 36
+draw_map(move_knots(example2, 10))
 @info part_2(input)