require_relative 'util'

# --- Day 3: Squares With Three Sides ---

# Now that you can think clearly, you move deeper into the labyrinth
# of hallways and office furniture that makes up this part of Easter
# Bunny HQ. This must be a graphic design department; the walls are
# covered in specifications for triangles.

# Or are they?

# The design document gives the side lengths of each triangle it
# describes, but... 5 10 25? Some of these aren't triangles. You can't
# help but mark the impossible ones.

# In a valid triangle, the sum of any two sides must be larger than
# the remaining side. For example, the "triangle" given above is
# impossible, because 5 + 10 is not larger than 25.

# In your puzzle input, how many of the listed triangles are possible?

input = File.open('03.txt') do |f|
  f.readlines.map { |line| line.scan(/\d+/) .map(&:to_i) }
end

def valid_triangle?(a, b, c)
  ((a + b) > c) && ((a + c) > b) && ((b + c) > a)
end

assert(!valid_triangle?(5, 10, 25))

def easy(input)
  input.count { |a, b, c| valid_triangle?(a, b, c) }
end

puts "easy(input): #{easy(input)}"

# --- Part Two ---

# Now that you've helpfully marked up their design documents, it
# occurs to you that triangles are specified in groups of three
# vertically. Each set of three numbers in a column specifies a
# triangle. Rows are unrelated.

# For example, given the following specification, numbers with the
# same hundreds digit would be part of the same triangle:

#     101 301 501
#     102 302 502
#     103 303 503
#     201 401 601
#     202 402 602
#     203 403 603

# In your puzzle input, and instead reading by columns, how many of
# the listed triangles are possible?

def hard(input)
  count = 0
  input.transpose.each do |row|
    count += row.each_slice(3).count { |a, b, c| valid_triangle?(a, b, c) }
  end
  count
end

puts "hard(input): #{hard(input)}"