DavidEGrayson · December 15, 2022 04:55 · Dec 15, 2022 · Dec 15, 2022
diff --git a/hashset.rb b/hashset.rb
@@ -0,0 +1,122 @@
+# SLOWER VERSION OF MY CODE that uses a "hash set".
+
+$width = 1000
+$height = 200
+$rocks = {}
+$sand = {}
+
+def coords_in_bounds?(coords)
+  (0...$width).include?(coords[0]) && (0...$height).include?(coords[1])
+end
+
+def read(coords)
+  return '#' if $rocks[coords]
+  return 'o' if $sand[coords]
+  ' '
+end
+
+def draw(coords, char)
+  raise if !coords_in_bounds?(coords)
+  #$rocks.delete(coords)
+  #$sand.delete(coords)
+  $rocks[coords.dup.freeze] = true if char == '#'
+  $sand[coords.dup.freeze] = true if char == 'o'
+end
+
+def draw_rock_line(start, dest)
+  start = start.dup
+  while true
+    draw(start, '#')
+    if start[0] < dest[0]
+      start[0] += 1
+    elsif start[0] > dest[0]
+      start[0] -= 1
+    elsif start[1] < dest[1]
+      start[1] += 1
+    elsif start[1] > dest[1]
+      start[1] -= 1
+    else
+      break
+    end
+  end
+end
+
+# NOT NEEDED TO SOLVE THE PROBLEM.  This is just for testing the slow/naive way.
+def add_sand(start)
+  coords = start
+  while true
+    grain_fell = false
+
+    support_coords = [
+      [coords[0], coords[1] + 1],
+      [coords[0] - 1, coords[1] + 1],
+      [coords[0] + 1, coords[1] + 1],
+    ]
+    support_coords.each do |sc|
+      return false if !coords_in_bounds?(sc)
+      if read(sc) == ' '
+        coords = sc
+        grain_fell = true
+        break
+      end
+    end
+
+    if !grain_fell
+      draw(coords, 'o')
+      return true
+    end
+  end
+end
+
+# NOT NEEDED TO SOLVE THE PROBLEM.  This is just for testing the slow/naive way.
+def slow_fill(coords)
+  while read(coords) == ' '
+    add_sand(coords) or return
+  end
+end
+
+# Fast recursive function that tries to place a sand grain at the specified
+# point by recursively filling the three spots in the row below that support it.
+# Returns true if successful.
+def fill(coords)
+  x, y = coords
+  if !coords_in_bounds?(coords)
+    false
+  elsif '#o'.include?(read(coords))
+    true
+  elsif fill([x, y + 1]) && fill([x - 1, y + 1]) && fill([x + 1, y + 1])
+    draw(coords, 'o')
+    true
+  else
+    draw(coords, '~')
+    false
+  end
+end
+
+File.foreach('input.txt') do |line|
+  coord_strings = line.split(' -> ')
+  coords = nil
+  coord_strings.each do |coord_string|
+    next_coords = coord_string.split(',').map(&:to_i)
+    raise if next_coords.size != 2
+    draw_rock_line(coords, next_coords) if coords
+    coords = next_coords
+  end
+end
+
+# Part 2, with hardcoded floor height.
+draw_rock_line([0, 184], [$width - 1, 184])
+
+# fill([500, 0])
+slow_fill([500, 0])
+
+#$world.each_line { |line| puts line[450..600] }
+(0...$height).each do |y|
+  (450...600).each do |x|
+    print read([x, y])
+  end
+  puts
+end
+
+
+puts $sand.size
diff --git a/advent.rb b/advent.rb
@@ -0,0 +1,106 @@
+$width = 1000
+$height = 200
+$world = (' ' * $width + "\n") * $height
+
+def coords_in_bounds?(coords)
+  (0...$width).include?(coords[0]) && (0...$height).include?(coords[1])
+end
+
+def read(coords)
+  raise if !coords_in_bounds?(coords)
+  $world[coords[1] * ($width + 1) + coords[0]]
+end
+
+def draw(coords, char)
+  raise if !coords_in_bounds?(coords)
+  $world[coords[1] * ($width + 1) + coords[0]] = char
+end
+
+def draw_rock_line(start, dest)
+  start = start.dup
+  while true
+    draw(start, '#')
+    if start[0] < dest[0]
+      start[0] += 1
+    elsif start[0] > dest[0]
+      start[0] -= 1
+    elsif start[1] < dest[1]
+      start[1] += 1
+    elsif start[1] > dest[1]
+      start[1] -= 1
+    else
+      break
+    end
+  end
+end
+
+# NOT NEEDED TO SOLVE THE PROBLEM.  This is just for testing the slow/naive way.
+def add_sand(start)
+  coords = start
+  while true
+    grain_fell = false
+
+    support_coords = [
+      [coords[0], coords[1] + 1],
+      [coords[0] - 1, coords[1] + 1],
+      [coords[0] + 1, coords[1] + 1],
+    ]
+    support_coords.each do |sc|
+      return false if !coords_in_bounds?(sc)
+      if read(sc) == ' '
+        coords = sc
+        grain_fell = true
+        break
+      end
+    end
+
+    if !grain_fell
+      draw(coords, 'o')
+      return true
+    end
+  end
+end
+
+# NOT NEEDED TO SOLVE THE PROBLEM.  This is just for testing the slow/naive way.
+def slow_fill(coords)
+  add_sand(coords) while read(coords) == ' '
+end
+
+# Fast recursive function that tries to place a sand grain at the specified
+# point by recursively filling the three spots in the row below that support it.
+# Returns true if successful.
+def fill(coords)
+  x, y = coords
+  if !coords_in_bounds?(coords)
+    false
+  elsif '#o'.include?(read(coords))
+    true
+  elsif fill([x, y + 1]) && fill([x - 1, y + 1]) && fill([x + 1, y + 1])
+    draw(coords, 'o')
+    true
+  else
+    draw(coords, '~')
+    false
+  end
+end
+
+File.foreach('input.txt') do |line|
+  coord_strings = line.split(' -> ')
+  coords = nil
+  coord_strings.each do |coord_string|
+    next_coords = coord_string.split(',').map(&:to_i)
+    raise if next_coords.size != 2
+    draw_rock_line(coords, next_coords) if coords
+    coords = next_coords
+  end
+end
+
+# Part 2, with hardcoded floor height.
+draw_rock_line([0, 184], [$width - 1, 184])
+
+fill([500, 0])
+# slow_fill([500, 0])
+
+$world.each_line { |line| puts line[450..600] }
+
+puts $world.count('o')