day 15, part 1

Author: Robb Kidd

2023/ruby/day15.rb

@@ -0,0 +1,57 @@
+require_relative 'day'
+
+class Day15 < Day # >
+
+  # @example
+  #   day.part1 #=> 1320
+  def part1
+    initialization_sequence
+      .reduce(0) { |sum, step| sum += HASH.hash(step) }
+  end
+
+  # example
+  #   day.part2 #=> 'how are you'
+  def part2
+  end
+
+  # @example parses_input
+  #   h = new(Day15::EXAMPLE_INPUT)
+  #   h.initialization_sequence #=> %w{rn=1 cm- qp=3 cm=2 qp- pc=4 ot=9 ab=5 pc- pc=6 ot=7}
+  def initialization_sequence
+    @initialization_sequence ||=
+      input.tr("\n", "").split(",")
+  end
+
+  EXAMPLE_INPUT = <<~INPUT
+    rn=1,cm-,qp=3,cm=2,qp-,pc=4,ot=9,ab=5,pc-,pc=6,ot=7
+  INPUT
+end
+
+#class Holiday_ASCII_String_Helper
+module HASH
+  # @example
+  #   HASH.hash("") #=> 0
+  # @example HASH
+  #   HASH.hash("HASH") #=> 52
+  # @example from_example_input
+  #   HASH.hash("rn=1") #=> 30
+  #   HASH.hash("cm-") #=> 253
+  #   HASH.hash("qp=3") #=> 97
+  #   HASH.hash("cm=2") #=> 47
+  #   HASH.hash("qp-") #=> 14
+  #   HASH.hash("pc=4") #=> 180
+  #   HASH.hash("ot=9") #=> 9
+  #   HASH.hash("ab=5") #=> 197
+  #   HASH.hash("pc-") #=> 48
+  #   HASH.hash("pc=6") #=> 214
+  #   HASH.hash("ot=7") #=> 231
+  def self.hash(str="")
+    str
+      .each_byte             # Determine the ASCII code for the current character of the string.
+      .inject(0) do |current_value, ord| # start with a current value of 0
+        current_value += ord # Increase the current value by the ASCII code you just determined.
+        current_value *= 17  # Set the current value to itself multiplied by 17.
+        current_value %= 256 # Set the current value to the remainder of dividing itself by 256.
+      end
+  end
+end