Difference between revisions of "Counting sort"
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| − | The counting sort is an integer sorting algorithm. | + | {{Counting_sort}} |
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| + | The counting sort is an [[Integer|integer]] [[sorting algorithm]]. | ||
== Features == | == Features == | ||
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== unit UCountingSortExtra.pas == | == unit UCountingSortExtra.pas == | ||
| − | <syntaxhighlight> | + | <syntaxhighlight lang="pascal"> |
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unit UCountingSortExtra; | unit UCountingSortExtra; | ||
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interface | interface | ||
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end; | end; | ||
| − | end. | + | end. |
| − | |||
</syntaxhighlight> | </syntaxhighlight> | ||
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== unit UCountingSort.pas == | == unit UCountingSort.pas == | ||
| − | <syntaxhighlight> | + | <syntaxhighlight lang="pascal"> |
| − | |||
unit UCountingSort; | unit UCountingSort; | ||
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interface | interface | ||
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if a[ i ] > max then max := a[ i ]; | if a[ i ] > max then max := a[ i ]; | ||
end; | end; | ||
| − | SetLength( count_a, max - min ); | + | SetLength( count_a, max - min + 1); |
for i := 0 to ( max - min ) do count_a[ i ] := 0; | for i := 0 to ( max - min ) do count_a[ i ] := 0; | ||
for i := low( a ) to high( a ) do | for i := low( a ) to high( a ) do | ||
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end; | end; | ||
| − | end. | + | end. |
</syntaxhighlight> | </syntaxhighlight> | ||
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== Example of the use == | == Example of the use == | ||
| − | <syntaxhighlight> | + | <syntaxhighlight lang="pascal"> |
uses | uses | ||
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var | var | ||
| − | a: array[0..100] of integer; | + | a: array[0..100] of integer; |
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</syntaxhighlight> | </syntaxhighlight> | ||
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Latest revision as of 20:29, 7 July 2019
│
English (en) │
français (fr) │
The counting sort is an integer sorting algorithm.
Features
- Very fast
- Only small integers
unit UCountingSortExtra.pas
unit UCountingSortExtra;
interface
type
// data type
TItemCountingSort=integer;
// sort order
function IsAscendingCountingSort: boolean; inline;
implementation
// sort order
function IsAscendingCountingSort: boolean; inline;
begin
result := true;
end;
end.
unit UCountingSort.pas
unit UCountingSort;
interface
uses
UCountingSortExtra;
// sorting function
procedure CountingSort( var a: array of TItemCountingSort );
implementation
procedure CountingSort( var a: array of TItemCountingSort );
var
min, max : TItemCountingSort;
count_a : array of integer;
i, j, z : integer;
begin
min := high( a );
max := min;
for i := low( a ) to high( a ) do
begin
if a[ i ] < min then min := a[ i ];
if a[ i ] > max then max := a[ i ];
end;
SetLength( count_a, max - min + 1);
for i := 0 to ( max - min ) do count_a[ i ] := 0;
for i := low( a ) to high( a ) do
count_a[ a[ i ] - min ] := count_a[ a[ i ] - min ] + 1;
if IsAscendingCountingSort then z:= low( a ) else z := high( a );
for i := min to max do
for j := 0 to ( count_a[ i - min ] - 1 ) do
begin
a[ z ] := i;
if IsAscendingCountingSort then inc( z ) else dec( z );
end;
end;
end.
Example of the use
uses
UCountingSort
...
var
a: array[0..100] of integer;
begin
...
CountingSort( a );
