gistfile1.rbx

# If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23.
# Find the sum of all the multiples of 3 or 5 below 1000.

def list_of_mults(from, multiple)
  from.select {|i| i % multiple == 0 }
end

def check_result(res, multiple)
  zeroes = res.collect {|i| i % multiple}
  bad_ones = zeroes.select {|i| i != 0}
  
  if bad_ones.length > 0
    raise "Wrong multiples in #{res.inspect}" 
  end
end

def sum_list(initial, list)
  list.inject(initial) {|h,g| h+g }
end  

start = (1..999).to_a

# All multiples of 3 and then all multiples of 5 in seperate lists ,add sum
x = list_of_mults(start, 3)
y = list_of_mults(start, 5)
  
check_result(x, 3)
check_result(y, 5)

y_sum = sum_list(0, y)
x_sum = sum_list(0, x)
total = sum_list(x_sum, y)

puts "x should be 63, y should be 50 sum should be 113"
puts "x == #{x_sum}, y=#{y_sum}, total=#{total}"