2022 day 5 part 1

Author: Robb Kidd

2022/ruby/day05.rb

@@ -0,0 +1,90 @@
+class Day05
+  def self.go
+    day = new
+    puts "Part 1: #{day.part1}"
+    puts "Part 2: #{day.part2}"
+  end
+
+  def initialize(input=nil)
+    @input = input || real_input
+    @stacks = parse_stacks
+    @moves = parse_moves
+  end
+
+  # @example
+  #   day.part1 => "CMZ"
+  def part1
+    @moves
+      .each { |step|
+        step[:quantity].times {
+          @stacks[step[:to]].push( @stacks[step[:from]].pop)
+        }
+      }
+
+    @stacks
+      .values
+      .map(&:last)
+      .join("")
+  end
+
+  def part2
+  end
+
+  # @example
+  #   day.parse_stacks => EXAMPLE_STACK_START
+  def parse_stacks
+    stacks_input, _ = @input.split("\n\n")
+
+    stacks_input
+      .split("\n")
+      .reverse
+      .map(&:chars)
+      .transpose
+      .select{ |stack| stack[0] != " " }
+      .each_with_object({}) { |stack_in, stacks|
+        stack_no = stack_in.shift
+        stacks[stack_no] = stack_in.select{|crate| crate != " "}
+      }
+  end
+
+  # @example
+  #   day.parse_moves => EXAMPLE_MOVES
+  def parse_moves
+    _, moves_input = @input.split("\n\n")
+    
+    moves_input
+      .split("\n")
+      .each_with_object([]) { |line, moves|
+        line.match(/move (\d+) from (\d+) to (\d+)/) { |matchdata|
+          moves << { quantity: matchdata[1].to_i, from: matchdata[2], to: matchdata[3] }
+        }
+      }
+  end
+
+  def real_input
+    File.read('../inputs/day05-input.txt')
+  end
+
+  EXAMPLE_STACK_START = {
+    "1" => %w[Z N],
+    "2" => %w[M C D],
+    "3" => %w[P],
+  }
+  EXAMPLE_MOVES = [
+    { quantity: 1, from: "2", to: "1" },
+    { quantity: 3, from: "1", to: "3" },
+    { quantity: 2, from: "2", to: "1" },
+    { quantity: 1, from: "1", to: "2" },
+  ]
+  EXAMPLE_INPUT = <<~INPUT
+        [D]    
+    [N] [C]    
+    [Z] [M] [P]
+     1   2   3 
+    
+    move 1 from 2 to 1
+    move 3 from 1 to 3
+    move 2 from 2 to 1
+    move 1 from 1 to 2
+  INPUT
+end