Extracting the shortest string from an array

[Iñaki Baz Castillo]

Hi, given the following array:

array =3D ["qwe", "qwerty"]

How to get the shortest element ("qwe") from the array?
I whink I must inspect all the elements within the array and manually
select the shortest string, do I miss some cool feature of Array class
or Enumerable module?

Thanks a lot.

--=20
I=C3=B1aki Baz Castillo
<[email protected]>

 

[Adam Hegge]

array.min{|a,b| a.size <=> b.size }

 

[Thorsten Hater]

Hi,

in Ruby 1.9 this should work:

arr.sort_by(&:length)[0]

or more portable/readable (1.8 compatible):

arr.sort_by{|s| s.length }[0]


Am 03.03.2011 15:47, schrieb Iñaki Baz Castillo:

 

[Paul McKibbin]

Hi,

You could use

array.min {|x,y| x.size <=3D> y.size}

to force a min to use sizes rather then their natural order

Mac

 

[Iñaki Baz Castillo]

Hi,

You could use

array.min {|x,y| x.size <=3D> y.size}

to force a min to use sizes rather then their natural order

Thanks to all

--=20
I=C3=B1aki Baz Castillo
<[email protected]>

 

[Jeremy Bopp]

array.min{|a,b| a.size <=> b.size }

You can actually simplify this even more. Take a look at Enumerable#min_by:

http://rdoc.info/stdlib/core/1.8.7/Enumerable:min_by

-Jeremy

 

[Robert Klemme]

in Ruby 1.9 this should work:

arr.sort_by(&:length)[0]

Inefficient as it creates a new array. Better do

irb(main):001:0> ["qwe", "qwerty"].min_by(&:length)
=> "qwe"

or more portable/readable (1.8 compatible):

arr.sort_by{|s| s.length }[0]

Inefficient as well (see above).

Cheers

robert

 

[Paul McKibbin]

[Note: parts of this message were removed to make it a legal post.]

Very true

array.min_by{|a| a.size} would also do the trick.

Paul

 

[Josh Cheek]

[Note: parts of this message were removed to make it a legal post.]

in Ruby 1.9 this should work:

arr.sort_by(&:length)[0]

Inefficient as it creates a new array. Better do

irb(main):001:0> ["qwe", "qwerty"].min_by(&:length)
=> "qwe"


or more portable/readable (1.8 compatible):

arr.sort_by{|s| s.length }[0]

Inefficient as well (see above).

Cheers

robert

They're also O( n lg n ) where the correct solution, using min, is O(n)

 

[Robert Klemme]

in Ruby 1.9 this should work:

=A0 =A0arr.sort_by(&:length)[0]

Inefficient as it creates a new array. =A0Better do

irb(main):001:0> ["qwe", "qwerty"].min_by(&:length)
=3D> "qwe"


=A0or more portable/readable (1.8 compatible):

=A0 =A0arr.sort_by{|s| s.length }[0]

Inefficient as well (see above).

They're also O( n lg n ) where the correct solution, using min, is O(n)

How do you know that it's O(n * log n)? A reasonable implementation
of min_by would look like this:

def min_by(enum, &c)
min =3D nil
val =3D nil

enum.each do |e|
e_val =3D c[e]

if val.nil? || e_val < val
min =3D e
val =3D e_val
end
end

min
end

As far as I can see this is O(n).

Also, big O isn't everything. Usually object allocation is very
expensive (compared to other operations) because of the GC
housekeeping overhead.

Cheers

robert

--=20
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/

 

[Josh Cheek]

[Note: parts of this message were removed to make it a legal post.]

On 03.03.2011 16:02, Thorsten Hater wrote:

in Ruby 1.9 this should work:

arr.sort_by(&:length)[0]


Inefficient as it creates a new array. Better do

irb(main):001:0> ["qwe", "qwerty"].min_by(&:length)
=> "qwe"


or more portable/readable (1.8 compatible):

arr.sort_by{|s| s.length }[0]


Inefficient as well (see above).

They're also O( n lg n ) where the correct solution, using min, is O(n)

How do you know that it's O(n * log n)? A reasonable implementation
of min_by would look like this:

def min_by(enum, &c)
min = nil
val = nil

enum.each do |e|
e_val = c[e]

if val.nil? || e_val < val
min = e
val = e_val
end
end

min
end

As far as I can see this is O(n).

Right. This was my point: using min is O(n), using sort is O(n lg n)

Also, big O isn't everything. Usually object allocation is very
expensive (compared to other operations) because of the GC
housekeeping overhead.

I don't contest this. I was pointing out that in addition to creating more
objects, as you previously mentioned, using sort also has a worse time
complexity.

 

[Robert Klemme]

On Thu, Mar 3, 2011 at 11:35 AM, Robert Klemme

On 03.03.2011 16:02, Thorsten Hater wrote:

in Ruby 1.9 this should work:

=A0 =A0arr.sort_by(&:length)[0]


Inefficient as it creates a new array. =A0Better do

irb(main):001:0> ["qwe", "qwerty"].min_by(&:length)
=3D> "qwe"


=A0or more portable/readable (1.8 compatible):

=A0 =A0arr.sort_by{|s| s.length }[0]


Inefficient as well (see above).

They're also O( n lg n ) where the correct solution, using min, is O(n=

)

Right. This was my point: using min is O(n), using sort is O(n lg n)

OK, now I get what you mean. You were referring to the sorts. That
wasn't clear to me.

I don't contest this. I was pointing out that in addition to creating mor= e
objects, as you previously mentioned, using sort also has a worse time
complexity.

Yep, sorry for the noise.

Cheers

robert


--=20
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/