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From: =?UTF-8?Q?Arne_Vajh=c3=b8j?= <arne@vajhoej.dk>
Newsgroups: comp.lang.java.programmer
Subject: Re: How to parse an array?
Date: Tue, 20 Jun 2017 16:15:57 -0400
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On 6/20/2017 3:18 PM, Eric Douglas wrote:
> I'm writing a method to take 2 arrays and return the subset of the first array.
> Is there a more efficient way than creating a new array and iterating?
> 
> ArrayList<String> list1 = new ArrayList();
> list1.add("AA");
> list1.add("CC");
> list1.add("DD");
> list1.add("BB");
> list1.add("EE");
> ArrayList<Integer> list2 = new ArrayList();
> list2.add(1);
> list2.add(3);
> ArrayList<String> retval = new ArrayList();
> for (int i : list2) {
>       retval.add(list1.get(i));
> }
> Collections.sort(retval);
> System.out.println(retval);

The problems must be O(n) in both list sizes.

Your code is O(n).

And your code is easy to read.

I don't see any urgent need to do it differently.

Arne