Re: Array sort problem.

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From	Lew <lewbloch@gmail.com>
Newsgroups	comp.lang.java.help
Subject	Re: Array sort problem.
Date	Mon, 17 Oct 2011 15:54:50 -0700 (PDT)
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Alex Mentis wrote:
> Warren Tang wrote:
>> I have an array:
>> 
>> index value
>> 0	33
>> 1	22
>> 2	44
>> 3	11
>> 
>> Now I'd like to sort it, but I also need to preserve the original
>> index, like this:
>> 
>> newIndex originalIndex sortedValue
>> 0	3	11
>> 1	1	22
>> 2	0	33
>> 3	2	44
>> 
>> How can this be done conveniently in Java?
> 
> I imagine you'd have to go through the array of values and turn it into
> an array of objects that contain fields for both the original index and
> value. Then sort the new array based on the values.

+1

Here's a rough outline of such a (value,index) type (not compiled, untried):

 public class ValueIndex<T extends Comparable> 
        implements Comparable<ValueIndex<T>>
 {
   private final T value;
   private final int index;
   public ValueIndex( T val, int idx )
   {
     if (val == null) {throw new IllegalArgumentException("null value");}
     this.value = val;
     this.index = idx;
     assert this.value != null;
   }
   public T getValue() {assert value != null; return value;}
   public int getIndex() {return index;}
   @Override public int compareTo(ValueIndex<T> other)
   {
     return other == null ? 1 : getValue().compareTo( other.getValue() );
   }
 }


-- 
Lew

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Thread

Array sort problem. Warren Tang <nospam@tangcs.com> - 2011-10-18 03:42 +0800
  Re: Array sort problem. "Alex Mentis" <foo@invalid.invalid> - 2011-10-17 21:14 +0000
    Re: Array sort problem. Lew <lewbloch@gmail.com> - 2011-10-17 15:54 -0700
      Re: Array sort problem. Warren Tang <nospam@tangcs.com> - 2011-10-19 10:59 +0800
  Re: Array sort problem. Roedy Green <see_website@mindprod.com.invalid> - 2011-10-19 15:22 -0700

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