Question

I am trying to sort large inputs in the fastest way in ascending order. The code is something like this:

t=gets
ti=t.to_i
r=[]
for i in(0..ti)
    k=gets
    r[i]=k.to_i
end
r.sort_by{|x| -x.last}

This is giving me an error saying undefined method 'last' for nil:nilclass <nomethoderror>
from tsort.rb: in sort_by
from tsort.rb in 'each'
from tsort.rb in 'sort_by'

I don’t know where am I wrong.

That’s what I have tried for sorting an array…which is r[] which has all the numbers in t! Can anyone please help.

My inputs are less than 10^6!

Answer 1

I can’t reproduce your exact error, I get undefined method 'last' for n:Fixnum (NoMethodError). That makes sense, because you’re calling the last method on x, which will hold the values of your Array r, all Fixnums, which do not have a last method.

It should work if you replace the last line with:

r.sort

The sort method will sort your Array in ascending order by default.