Question

I need to group numbers that are in numerical order from an array.

(using ruby 1.9.2, rails 3.2)

Example1:
[1,2,4,5,6]

Example2:
[1,3,4,6,7]

Example3:
[1,2,3,5,6]

Example4:
[1,2,4,5,7]

After grouping

Example1:
[[1,2],[4,5,6]]

Example2:
[[1],[3,4],[6,7]]

Example3:
[[1,2,3],[5,6]]

Example4:
[[1,2],[4,5],[7]]

You get the idea.
(What I’m actually doing is grouping days, not relevant though)

Thanks in advance!

Answer 1

I’m not sure what you’d call this operation, but it’s a sort of grouping method based on the last element processed. Something like:

def groupulate(list)
  list.inject([ ]) do |result, n|
    if (result[-1] and result[-1][-1] == n - 1)
      result[-1] << n
    else
      result << [ n ]
    end

    result
  end
end

The Enumerable module provides a large number of utility methods for processing lists, but inject is the most flexible by far.