Ruby Print Pyramid with 2D array (stuck in infinite loop)

bbachman

Trying to create a pyramid with a 2D Array, they give us the bottom row of the pyramid. We get the next rows by adding the numbers of the row below. Cannot seem to get the top number of the pyramid. Goes into an infinite loop.

Here is the description of the assignment:

"Pyramid Sum
Write a method pyramid_sum that takes in an array of numbers representing the base of a pyramid. The function should return a 2D array representing a complete pyramid with the given base. To construct a level of the pyramid, we take the sum of adjacent elements of the level below."

def pyramid_sum(base)
  new_array = []
  sub_array =[]
  temp_array = base
  loop do
    # temp_array = [5, 10]
    puts "Top"
    print temp_array
    puts
    puts 
    temp_array.each_with_index do |num, idx|
      puts ".each loop"
     if idx+1 < temp_array.length 
        puts "adding..."
       sum = temp_array[idx] + temp_array[idx+1]
       sub_array << sum
     end # sub_array = [15]
    end
    puts "End of .each"
    new_array << sub_array
    temp_array = sub_array
    puts "Bottom"
    print temp_array
    puts
    puts 
    if temp_array.length == 1
     break
    end
  end
  return new_array
end

print pyramid_sum([1, 4, 6]) #=> [[15], [5, 10], [1, 4, 6]]
puts

#print pyramid_sum([3, 7, 2, 11]) #=> [[41], [19, 22], [10, 9, 13], [3, 7, 2, 11]]
#puts

avan

Hey, I think I figured it out. There are three changes that needs to be done in order to get the results you are looking for.

new_array has to be initialized to whatever the user provides for base
sub_array needs to be set to an empty array every-time it used to add to new_array
The last step is just to reverse the final array new_array so it looks like what they expect the results to be

Here is working version:

def pyramid_sum(base)
  new_array = []
  sub_array =[]
  temp_array = base
  # Change 1
  new_array << base
  loop do
    temp_array.each_with_index do |num, idx|
     if idx+1 < temp_array.length 
       sum = temp_array[idx] + temp_array[idx+1]
       sub_array << sum
     end # sub_array = [15]
    end
    new_array << sub_array
    temp_array = sub_array
    # Change 2
    sub_array = []
    if temp_array.length == 1
     break
    end
  end
  # Change 3 
  return new_array.reverse
end

avan

Hey, I think I figured it out. There are three changes that needs to be done in order to get the results you are looking for.

new_array has to be initialized to whatever the user provides for base
sub_array needs to be set to an empty array every-time it used to add to new_array
The last step is just to reverse the final array new_array so it looks like what they expect the results to be

Here is working version:

def pyramid_sum(base)
  new_array = []
  sub_array =[]
  temp_array = base
  # Change 1
  new_array << base
  loop do
    temp_array.each_with_index do |num, idx|
     if idx+1 < temp_array.length 
       sum = temp_array[idx] + temp_array[idx+1]
       sub_array << sum
     end # sub_array = [15]
    end
    new_array << sub_array
    temp_array = sub_array
    # Change 2
    sub_array = []
    if temp_array.length == 1
     break
    end
  end
  # Change 3 
  return new_array.reverse
end

bbachman

Thanks Avan!