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    <p>Answer to the second question: Mergesort modification with duplicate deleting. Should work for strings.</p> <pre><code>//returns new valid length function MergeSortRemoveDuplicates(var Vals: array of Integer):Integer; var AVals: array of Integer; //returns index of the last valid element function Merge(I0, I1, J0, J1: Integer):Integer; var i, j, k, LC:Integer; begin LC := I1 - I0; for i := 0 to LC do AVals[i]:=Vals[i + I0]; //copy lower half or Vals into temporary array AVals k := I0; i := 0; j := J0; while ((i &lt;= LC) and (j &lt;= J1)) do if (AVals[i] &lt; Vals[j]) then begin Vals[k] := AVals[i]; inc(i); inc(k); end else if (AVals[i] &gt; Vals[j]) then begin Vals[k]:=Vals[j]; inc(k); inc(j); end else begin //duplicate Vals[k] := AVals[i]; inc(i); inc(j); inc(k); end; //copy the rest while i &lt;= LC do begin Vals[k] := AVals[i]; inc(i); inc(k); end; if k &lt;&gt; j then while j &lt;= J1 do begin Vals[k]:=Vals[j]; inc(k); inc(j); end; Result := k - 1; end; //returns index of the last valid element function PerformMergeSort(ALo, AHi:Integer): Integer; //returns var AMid, I1, J1:Integer; begin //It would be wise to use Insertion Sort when (AHi - ALo) is small (about 32-100) if (ALo &lt; AHi) then begin AMid:=(ALo + AHi) shr 1; I1 := PerformMergeSort(ALo, AMid); J1 := PerformMergeSort(AMid + 1, AHi); Result := Merge(ALo, I1, AMid + 1, J1); end else Result := ALo; end; begin SetLength(AVals, Length(Vals) div 2 + 1); Result := 1 + PerformMergeSort(0, High(Vals)); end; //short test var A: array of Integer; i, NewLen: Integer; begin Randomize; SetLength(A, 12); for i := 0 to High(A) do A[i] := Random(10); NewLen := MergeSortRemoveDuplicates(A); SetLength(A, NewLen); for i := 0 to High(A) do Memo1.Lines.Add(IntToStr(A[i])) end; </code></pre> <p>Simple modification for strings:</p> <pre><code>function MergeSortRemoveDuplicates(var Vals: array of String):Integer; var AVals: array of String; </code></pre> <p>and test case:</p> <pre><code>var List: TStringList; Arr: array of string; i, n: Integer; begin with TStringList.Create do try LoadFromFile('F:\m2.txt'); //contains some equal strings SetLength(Arr, Count); for i := 0 to Count - 1 do Arr[i] := Strings[i]; finally Free end; n := MergeSortRemoveDuplicates(Arr); for i := 0 to n - 1 do Memo1.Lines.Add(Arr[i]); end; </code></pre>
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    1. POdelphi mergesort for string arrays
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    1. POdelphi mergesort for string arrays
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    1. COthis is great if you can pass strings to it. The problem is that even your test case is integers. Thank you.
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      1. USMerlin W.
    2. COI see no problem with so simple modification. Added.
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    3. COThank you. I think I see the problem I'm having: my strings are not equal in length or even character set at times. Thank you again.
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      1. USMerlin W.
 

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