Question

Hey ,Guys ,I have a question. I want to transform the array.[[1, [-1, 1]], [1, [20, 8]], [1, [30, 4]], [1, [40, 2]], [1, [41, 6]], [1, [70, 243]]] into this style [1,[[-1,1],[20,8],[30,4]...] or a hash [1=>…]
How can i do this trick? thank you !

Answer 1

Dict method:

array = [your array]
dict = {}
array.each{ |a| (dict[a[0]] ||= []) << a[1] }

For clarity Chuck’s suggestion would bring this to:

array = [your array]
dict = Hash.new {|h,k| h[k] = []}
array.each{ |a| dict[a[0]] << a[1] }

You can then get an array from this in the style you want by doing:

new_arr = dict.select{|k,v| [k, v]}

Which will give you:

[[1, [[-1, 1], [20, 8], [30, 4], [40, 2], [41, 6], [70, 243]]]]

Notice the extra array, because if you had arrays begining with 2 you’d have another set at the end. So new_arr[0] will give you the array you were originally looking for.