implemented day 3 part 1.

src/advent/day3.rb

@@ -0,0 +1,137 @@
+# frozen_string_literal: true
+
+def group_neighbour(lst, &block)
+  if lst.empty?
+    return []
+  end
+  ret = [[lst[0]]]
+  lst.each_cons(2) do |first_and_second|
+    first, second = first_and_second
+    if block.call first, second
+      ret[-1].append second
+    else
+      ret.append [second]
+    end
+  end
+  ret
+end
+
+class EngineNumber
+  def initialize(line_index, start, end_, value)
+    @line_index = line_index
+    @start = start
+    @end_ = end_
+    @value = value
+  end
+
+
+  attr_accessor :line_index
+  attr_accessor :start
+  attr_accessor :end_
+  attr_accessor :value
+
+end
+
+class EngineLine
+  def initialize(idx, line)
+    @idx = idx
+    @line = line
+  end
+
+  def is_symbols?(letter)
+    unless letter
+      return false
+    end
+    "1234567890.".index(letter) == nil
+  end
+
+  def has_any_symbols_at(indexes)
+    indexes.any? do |idx|
+      is_symbols? @line[idx]
+    end
+  end
+
+  def extract_digit_indexes(word)
+    digit_indexes = []
+    word.split("").each_with_index do |letter, index|
+      if "0123456789".index letter
+        digit_indexes.append index
+      end
+    end
+    digit_indexes
+  end
+
+  def group_digit_indexes(digit_indexes)
+    group_neighbour(digit_indexes) {|x, y| y == x + 1}
+  end
+
+  def create_engine_number(digit_group)
+    start = digit_group.min
+    end_ = 1 + digit_group.max
+    value = @line[start...end_].to_i
+    EngineNumber.new @idx, start, end_, value
+  end
+
+  def extract_engine_numbers
+    digit_indexes = extract_digit_indexes @line
+    group_digit_indexes(digit_indexes).map &method(:create_engine_number)
+  end
+
+end
+
+class Engine
+  def initialize(engine_lines)
+    @engine_lines = engine_lines
+  end
+
+  def self.deserialize(ser)
+    els = ser.strip.split("\n").each_with_index.map { |line, idx| EngineLine.new idx, line}
+    return self.new els
+  end
+
+  def extract_engine_numbers
+    @engine_lines
+      .map {|line| line.extract_engine_numbers}
+      .flatten
+  end
+
+  def has_symbol?(line_index, indexes_in_line)
+    # indexes_in_line = indexes_in_line || []
+    # puts "> #{ indexes_in_line }"
+    @engine_lines[line_index]&.has_any_symbols_at indexes_in_line
+  end
+
+  def get_engine_number_neighbourhood(engine_number)
+    line_index = engine_number.line_index
+    [
+      {line_index: line_index, indexes_in_line: ((engine_number.start-1)..(engine_number.start-1))},
+      {line_index: line_index, indexes_in_line: ((engine_number.end_)..(engine_number.end_))},
+      {line_index: line_index - 1 , indexes_in_line: ((engine_number.start - 1)...(engine_number.end_+1))},
+      {line_index: line_index + 1 , indexes_in_line: ((engine_number.start - 1)...(engine_number.end_+1))},
+    ]
+
+  end
+
+  def touches_symbol?(engine_number)
+    get_engine_number_neighbourhood(engine_number).map do |h|
+      has_symbol?(h[:line_index], h[:indexes_in_line])
+    end
+    .any?
+  end
+
+  def extract_engine_numbers_that_touches_symbols
+    extract_engine_numbers.filter {|engine_number| touches_symbol? engine_number}
+  end
+
+  attr_accessor :engine_lines
+end
+
+
+input_file_name = File.join(File.dirname(__FILE__), "day_3_input.txt")
+
+input_content = File.open(input_file_name).read
+
+engine = Engine.deserialize input_content
+
+puts engine.extract_engine_numbers_that_touches_symbols.map {|e| e.value} .sum
+