```Hi,

2014-03-05 17:31 GMT+09:00 Robert Klemme <shortcutter / googlemail.com>:
> On Wed, Mar 5, 2014 at 8:42 AM, Heesob Park <phasis / gmail.com> wrote:
>
>> arr_even,arr_odd=arr.each_with_index.partition{|v|v[1].even?}.map{|v|v.map{|v|v[0]}}
>
> We can be a bit more efficient memory wise by replacing #map with
> #each and #map!
>
> irb(main):008:0> arr.each_with_index.partition {|x,i| i.odd?}.each
> {|a| a.map!(&:first)}
> => [[11, :true, -22, [], "n"], [12, "a", 300, {}, "n-1"]]
>
> Here's another approach
>
> irb(main):014:0> arr.each_slice(2).each_with_object([[],[]])
> {|(a,b),(even,odd)| even << a; odd << b}
> => [[12, "a", 300, {}, "n-1"], [11, :true, -22, [], "n"]]
>
> irb(main):016:0> arr.each_with_index.each_with_object([[],[]])
> {|(x,i),(even,odd)| (i.odd? ? odd : even) << x}
> => [[12, "a", 300, {}, "n-1"], [11, :true, -22, [], "n"]]
>
> irb(main):023:0> arr.each_with_object([[],[]]).each_with_index {|(x,
> (even, odd)), i| (i.odd? ? odd : even) << x}
> => [[12, "a", 300, {}, "n-1"], [11, :true, -22, [], "n"]]
>
> In all cases just assign via multiple assignment:
>
> arr_even, arr_odd = expr...
>
I found a bit more compact and efficient way

irb(main):037:0> arr.partition.with_index{|x,i|i.odd?}
=> [[11, :true, -22, [], "n"], [12, "a", 300, {}, "n-1"]]

Regards,
Park Heesob
```