Help with qsort

[George A. Basar]

In article <1989Nov20.213702.20821 at agate.berkeley.edu>, ilan343 at violet.berkeley.edu writes:
> I am trying to use the standard C qsort routine to rank an array of
> floats.  I don't want to disturb the original data, so I tried the
> following:
> 
> a) Copy the addresses of each array element into an array of pointers.
> b) Invoke qsort on the array of pointers. 
> c) Print ranks by subtracting pointers

  No need for step c, the entries in rank are pointers which had been sorted
  based upon the values in data.

> 	printf ("%d %f %d \n", i, data[i], rank[i] - data);

  This should be
 	printf ("%d %f %f \n", i, data[i], *rank[i]);

  Since your compare checks the value in data, qsort swapped pointers in 
rank.  Printing out the values referenced by the elements in rank in
order, as above, gives a sorted list.


* George A. Basar                              (317)742-8799 (home)
* aic at mentor.cc.purdue.edu                     BASAR at PURCCVM.BITNET    
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