Sort using a custom comparator: Difference between revisions
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#('this' 'exercise' 'is' 'dumb') asSortedCollection |
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sortBlock: [:first :second | (second size = first size) ifFalse: [second size > first size] ifTrue: [first < second]] |
Revision as of 22:06, 13 September 2007
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, and in ascending lexicographic order for strings of equal length. Use a sorting facility provided by the language/library, combined with your own callback comparison function.
Note: Lexicographic order is case-insensitive.
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; with Ada.Characters.Handling; use Ada.Characters.Handling; 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 To_Lower(To_String(Strings(Left))) < To_Lower(To_String(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); }
Clean
import StdEnv less s1 s2 | size s1 > size s2 = True | size s1 < size s2 = False | otherwise = lower s1 < lower s2 where lower :: String -> String lower s = {toLower c \\ c <-: s} Start = sortBy less ["This", "is", "a", "set", "of", "strings", "to", "sort"]
Common Lisp
In Common Lisp, the sort function takes a predicate that is used as the comparator. This parameter can be any two-argument function. Common Lisp defines a case-insensitive predicate called string-lessp:
CL-USER> (defvar *strings* ("Cat" "apple" "Adam" "zero" "Xmas" "quit" "Level" "add" "Actor" "base" "butter")) *STRINGS* CL-USER> (sort *strings* #'string-lessp) ("Actor" "Adam" "add" "apple" "base" "butter" "Cat" "Level" "quit" "Xmas" "zero") CL-USER>
E
/** returns a if it is nonzero, otherwise b() */ def nonzeroOr(a, b) { return a.isZero().pick(b(), a) } ["Here", "are", "some", "sample", "strings", "to", "be", "sorted"] \ .sort(fn a, b { nonzeroOr(b.size().op__cmp(a.size()), fn { a.compareToIgnoreCase(b) }) })
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
Alternate definition of mycmp
using the Monoid
instance for Ordering
:
import Data.Monoid mycmp s1 s2 = mappend (compare (length s2) (length s1)) (compare (map toLower s1) (map toLower s2))
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"); ?>
Pop11
lvars ls = ['Here' 'are' 'some' 'sample' 'strings' 'to' 'be' 'sorted']; define compare(s1, s2); lvars k = length(s2) - length(s1); if k < 0 then return(true); elseif k > 0 then return(false); else return (alphabefore(uppertolower(s1), uppertolower(s2))); endif; enddefine;
syssort(ls, compare) -> ls;
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))
Ruby
The sort methods for Arrays can accept a block to be used as comparator.
strings = ["Here", "are", "some", "sample", "strings", "to", "be", "sorted"] strings.sort{|x,y|((lencomp=(y.length<=>x.length))==0 ? x<=>y : lencomp)}
Smalltalk
- ('this' 'exercise' 'is' 'dumb') asSortedCollection
sortBlock: [:first :second | (second size = first size) ifFalse: [second size > first size] ifTrue: [first < second]]