Sorting an array of array by a certain value in the inner array

Question

I have the following array:

test = [["E","188","12314","87235"],["B","1803","12314","87235"],["C","1508","12314","87235"]]

I want to sort the whole array by the second value in the inner arrays (188,1803,1508). So this is what I want to have.

test = [["E","188","12314","87235"],["C","1508","12314","87235"],["B","1803","12314","87235"]]

What would be the most efficient way to achieve this? Do I need to write a sort to do it?

The logic is not clear. If you sort them, the order should be "1508", "1803", "188". — sawa
– sawa, Commented Apr 15, 2016 at 15:43
What do you mean by the order should be "1508", "1803", "188"? I want them to be in ascending order. — Jack Li
– Jack Li, Commented Apr 15, 2016 at 15:54
Yes. ascending order. Just try it. ["188", "1803", "1508"].sort # => ["1508", "1803", "188"]. — sawa
– sawa, Commented Apr 15, 2016 at 15:55
Jack, @sawa is making the point that if you want the arrays sorted by the second elements after they are converted to integers, you've got to say that. You may think it's obvious, but it's not. Programming is all about precision, with your description of what you want to do or have done, as well as the code itself. — Cary Swoveland
– Cary Swoveland, Commented Apr 15, 2016 at 18:46

Maxim Pontyushenko · Accepted Answer · 2016-04-15 15:40:29Z

3

You can achieve it with sort_by:

test.sort_by { |e| e[1].to_i }

answered Apr 15, 2016 at 15:40

Maxim Pontyushenko

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Jack Li Over a year ago

Thanks! This helped a lot.

Cary Swoveland · Accepted Answer · 2016-04-15 18:50:38Z

1

Go with @Maxim's answer, but you could also write:

test.sort { |e,f| e[1].to_i <=> f[1].to_i }
  #=> [["E",  "188", "12314", "87235"],
  #    ["C", "1508", "12314", "87235"],
  #    ["B", "1803", "12314", "87235"]]

answered Apr 15, 2016 at 18:50

Cary Swoveland

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