SICP Exercise 1.12.rb

# Returns an array representing a specific level of Pascal's triangle
def pascal1(n)
  if n == 1
    [1]
  else
    nl = [0] + pascal1(n-1) + [0]
    l = []
    (nl.size - 1).times do |i|
      l << nl[i] + nl[i+1]
    end
    l
  end
end

# Returns the number at a specified level and index of Pascal's triangle
def pascal2(level,element)
  if element < 0 || element > level
    0
  elsif level == 0
    1
  else
    pascal2(level - 1, element - 1) + pascal2(level - 1, element)
  end  
end