Adku hiring puzzle

gistfile1.rb

def find_unique_paths(x, y, visited_points)
  if is_at_end_point?(x, y)
    @total_paths += 1 # successful path
  elsif !visited_points.include?([x, y])
    visited_points << [x, y] # unvisited point, add to path

    find_unique_paths(x + 1, y, visited_points.clone) if x + 1 <= @MAX_X # right
    find_unique_paths(x - 1, y, visited_points.clone) if x > 0           # left
    find_unique_paths(x, y + 1, visited_points.clone) if y + 1 <= @MAX_Y # down
    find_unique_paths(x, y - 1, visited_points.clone) if y > 0           # up
  end
end

def is_at_end_point?(x, y)
  [x, y] == [@MAX_X, @MAX_Y]
end

size_of_grid = ARGV[0].to_i
@total_paths = 0
# convert size into index values
@MAX_X = @MAX_Y = size_of_grid - 1

find_unique_paths(0, 0, [])

puts "Total number of unique paths for #{size_of_grid} x #{size_of_grid} grid is #{@total_paths}"