Sort using a custom comparator: Difference between revisions
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package Comparator_Package is |
package Comparator_Package is |
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procedure Move_String(From : Natural; To : Natural); |
procedure Move_String(From : Natural; To : Natural); |
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function Lt (Left, Right : Natural) return Boolean; |
function Lt (Left, Right : Natural) return Boolean; |
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procedure Print_Array; |
procedure Print_Array; |
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end Comparator_Package; |
end Comparator_Package; |
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Strings(To) := Strings(From); |
Strings(To) := Strings(From); |
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end Move_String; |
end Move_String; |
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function Lt (Left, Right : Natural) return Boolean is |
function Lt (Left, Right : Natural) return Boolean is |
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return Strings(Left) < Strings(Right); |
return Strings(Left) < Strings(Right); |
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end Lt; |
end Lt; |
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procedure Print_Array is |
procedure Print_Array is |
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Print_Array; |
Print_Array; |
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New_Line; |
New_Line; |
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Put_Line(" Sorted in descending |
Put_Line(" Sorted in descending length:"); |
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Sort(8, Move_String'access, |
Sort(8, Move_String'access, Len'access); |
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Print_Array; |
Print_Array; |
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New_Line; |
New_Line; |
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Put_Line(" Sorted in Ascending order:"); |
Put_Line(" Sorted in Ascending order:"); |
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Sort(8, Move_String'access, |
Sort(8, Move_String'access, Lt'access); |
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Print_Array; |
Print_Array; |
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end Custom_Comparator; |
end Custom_Comparator; |
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sort |
sort |
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Sorted in descending |
Sorted in descending length: |
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a |
a |
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is |
is |
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this |
this |
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to |
to |
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==[[C]]== |
==[[C]]== |
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[[Category:C]] |
[[Category:C]] |
Revision as of 03:20, 4 February 2007
Sort using a custom comparator
You are encouraged to solve this task according to the task description, using any language you may know.
You are encouraged to solve this task according to the task description, using any language you may know.
Sort an array (or list) of strings in order of descending length, then in ascending lexicographic order. Use a sorting facility provided by the language/library, combined with your own callback comparison function.
Ada
Compiler:GNAT GPL 2006
Comparator_Package.ads
package Comparator_Package is procedure Move_String(From : Natural; To : Natural); function Len (Left, Right : Natural) return Boolean; function Lt (Left, Right : Natural) return Boolean; procedure Print_Array; end Comparator_Package;
Comparator_Package.adb
with Ada.Strings.Unbounded; use Ada.Strings.Unbounded; with Ada.Text_Io; use Ada.Text_Io; package body Comparator_Package is type Data is array(Natural range <>) of Unbounded_String; Strings : Data := (Null_Unbounded_String, To_Unbounded_String("this"), To_Unbounded_String("is"), To_Unbounded_String("a"), To_Unbounded_String("set"), To_Unbounded_String("of"), To_Unbounded_String("strings"), To_Unbounded_String("to"), To_Unbounded_String("sort")); procedure Move_String(From : Natural; To : Natural) is begin Strings(To) := Strings(From); end Move_String; function Len (Left, Right : Natural) return Boolean is begin return Length(Strings(Left)) > Length(Strings(Right)); end Len; function Lt (Left, Right : Natural) return Boolean is begin return Strings(Left) < Strings(Right); end Lt; procedure Print_Array is begin for I in 1..Strings'Last loop Put_Line(To_String(Strings(I))); end loop; end Print_Array; end Comparator_Package;
Custom_Comparator.adb
with Gnat.Heap_Sort_A; use Gnat.Heap_Sort_A; with Ada.Text_Io; use Ada.Text_Io; with Comparator_Package; use Comparator_Package; procedure Custom_Comparator is begin Put_Line(" Unsorted Array:"); Print_Array; New_Line; Put_Line(" Sorted in descending length:"); Sort(8, Move_String'access, Len'access); Print_Array; New_Line; Put_Line(" Sorted in Ascending order:"); Sort(8, Move_String'access, Lt'access); Print_Array; end Custom_Comparator;
Output File
Unsorted Array: this is a set of strings to sort Sorted in descending length: strings sort this set to is of a Sorted in Ascending order: a is of set sort strings this to
C
Compiler: GCC 4.0.1
Platform: BSD
#include <stdlib.h> #include <strings.h> int mycmp(const void *s1, const void *s2) { int d; const char *l = *(const char **)s1, *r = *(const char **)s2; if (d = strlen(r) - strlen(l)) return d; return strcasecmp(l, r); } int main() { char *strings[8] = {"Here", "are", "some", "sample", "strings", "to", "be", "sorted"}; qsort(strings, 8, sizeof(char *), mycmp); }
Haskell
Interpreter: GHCi
import List import Char mycmp s1 s2 = case compare (length s2) (length s1) of EQ -> compare (map toLower s1) (map toLower s2) x -> x strings = ["Here", "are", "some", "sample", "strings", "to", "be", "sorted"] sorted = sortBy mycmp strings
Perl
Interpreter: perl 5.8.6
sub mycmp { length $b <=> length $a or lc $a cmp lc $b } @strings = ("Here", "are", "some", "sample", "strings", "to", "be", "sorted"); @sorted = sort mycmp @strings;
PHP
Interpreter: PHP 4.4.4 CLI
<?php function mycmp($s1, $s2) { if ($d = strlen($s2) - strlen($s1)) return $d; return strcasecmp($s1, $s2); } $strings = array("Here", "are", "some", "sample", "strings", "to", "be", "sorted"); usort($strings, "mycmp"); ?>
Python
Interpreter: 2.5
def mycmp(s1, s2): d = len(s2) - len(s1) return d if d else cmp(s1, s2) strings = ["Here", "are", "some", "sample", "strings", "to", "be", "sorted"] print sorted(strings, cmp=mycmp) # Alternative with decoration, unfit for very long lists: print sorted(strings, key=lambda s: (-len(s), s))