From: Rob Biedenharn <Rob@...>
Date: 2008-02-07T08:49:33+09:00
Subject: Re: Array Practice

On Feb 6, 2008, at 6:20 PM, Adam Akhtar wrote:

> As some of you may know from previous threads im trying to practice
> specific areas of ruby. One simple exercise i set myself was taking a
> elements in an array such as
>
> [1,2,3,1,2,2,4,3,2,1]
>
> and then grouping them together and putting them in subarrays within  
> an
> array like this
>
> [ [1,1,1], [2,2,2,2] , [3,3] ,[4] ]
>
> Heres how i did it (im new to both programming and ruby)
>
> def subpack(list)
>  uniqlist = Array.new
>  subpacklist = Array.new
>  list.sort!
>
>  uniqlist = list.uniq
>  uniqlist.each_index do |i|
>    rangeleft = list.index(uniqlist[i])
>    rangeright = list.rindex(uniqlist[i])
>    subpacklist << list.slice(rangeleft..rangeright)
>  end
>  subpacklist
> end
>
>
> WITHOUT GIVING ME YOUR SOLUTION IN FULL, how could i improve this...
> i.e. give me some hints, the names of some methods but not the  
> solution
> as i want a go myself.


Think about how you might do it with a pencil...
- write the values out in order "[ 1, 1, 1, 2, 2, 2, 2, 3, 3, 4 ]"
- if the "next" value is different from the last value processed (and  
initially there is no last value), then start a new sub-array with  
this single value (my pencil would insert a '[' between the '[' and '1')
- ...and if you'd already written a '[', you have to then  write "],["
- if the next value is the same, move your pencil (since it goes in  
the current sub-array)
- when you run out of values, close the final subarray with ']'

It shouldn't take much to think about how this turns into Ruby  
(keeping in mind that Arrays are always finite so you don't really  
have to "write" the ']')

-Rob

Rob Biedenharn		http://agileconsultingllc.com
Rob@AgileConsultingLLC.com