delphi mergesort for string arrays [closed]

Answer 1

1. You'd need to modify the declaration TSortArray from array of double to array of string (or array of MyRecord)

   The comparison routines in the Merge nested proc needs to be made compatible for strings. Check for anywhere that determines whether AVal[x] < / > AVal[y]. Delphi has procedures for this (AnsiCompareText / AnsiCompareStr depending on whether you want case-sensitivity)

   That should work, but if you hadn't done this in your earlier attempts then Delphi should have complained about type mismatches rather than giving an AV, so there may be something else going on

2. I think duplicate checking should be done post-sort - it only requires one scan through of the data

3. If you want to store original index data then you will probably need to use an array of record (data: string; OriginalIndex: integer). Code in the Merge procedure then needs to be modified to pass Vals[x].Data to comparison routines. Filling the OriginalIndex values will be a quick scan before calling the Merge procedure

4. Not 100% sure, to be honest - it's easier to move large contiguous chunks of data with linked lists than with arrays, and arrays don't need messing about with pointers. If your dataset is sufficiently large you may even need to resort to streaming to disk which is likely to drive your choice more than either of those points.