Sort using a custom comparator
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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.
[edit] Ada
with Ada.Text_Io; use Ada.Text_Io;
with Ada.Strings.Unbounded; use Ada.Strings.Unbounded;
with Gnat.Heap_Sort_G;
procedure Custom_Compare is
type StringArrayType is array (Natural range <>) of Unbounded_String;
Strings : StringArrayType := (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"),
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 (From, To : in Natural) is
begin
Strings(To) := Strings(From);
end Move;
function UpCase (Char : in Character) return Character is
Temp : Character;
begin
if Char >= 'a' and Char <= 'z' then
Temp := Character'Val(Character'Pos(Char)
- Character'Pos('a')
+ Character'Pos('A'));
else
Temp := Char;
end if;
return Temp;
end UpCase;
function Lt (Op1, Op2 : Natural)
return Boolean is
Temp, Len : Natural;
begin
Len := Length(Strings(Op1));
Temp := Length(Strings(Op2));
if Len < Temp then
return False;
elsif Len > Temp then
return True;
end if;
declare
S1, S2 : String(1..Len);
begin
S1 := To_String(Strings(Op1));
S2 := To_String(Strings(Op2));
Put("Same size: ");
Put(S1);
Put(" ");
Put(S2);
Put(" ");
for I in S1'Range loop
Put(UpCase(S1(I)));
Put(UpCase(S2(I)));
if UpCase(S1(I)) = UpCase(S2(I)) then
null;
elsif UpCase(S1(I)) < UpCase(S2(I)) then
Put(" LT");
New_Line;
return True;
else
return False;
end if;
end loop;
Put(" GTE");
New_Line;
return False;
end;
end Lt;
procedure Put (Arr : in StringArrayType) is
begin
for I in 1..Arr'Length-1 loop
Put(To_String(Arr(I)));
New_Line;
end loop;
end Put;
package Heap is new Gnat.Heap_Sort_G(Move,
Lt);
use Heap;
begin
Put_Line("Unsorted list:");
Put(Strings);
New_Line;
Sort(16);
New_Line;
Put_Line("Sorted list:");
Put(Strings);
end Custom_Compare;
[edit] Output
The output file looks like this:
Unsorted list:
this
is
a
set
of
strings
to
sort
This
Is
A
Set
Of
Strings
To
Sort
Sorted list:
strings
Strings
sort
Sort
this
This
Set
set
is
Is
Of
of
to
To
a
A
[edit] AutoHotkey
numbers = 5,3,7,9,1,13,999,-4
strings = Here,are,some,sample,strings,to,be,sorted
Sort, numbers, F IntegerSort D,
Sort, strings, F StringLengthSort D,
msgbox % numbers
msgbox % strings
IntegerSort(a1, a2) {
return a2 - a1
}
StringLengthSort(a1, a2){
return strlen(a1) - strlen(a2)
}
[edit] Burlesque
blsq ) {"acb" "Abc" "Acb" "acc" "ADD"}><
{"ADD" "Abc" "Acb" "acb" "acc"}
blsq ) {"acb" "Abc" "Acb" "acc" "ADD"}(zz)CMsb
{"Abc" "acb" "Acb" "acc" "ADD"}
[edit] C
#include <stdlib.h> /* for qsort */
#include <string.h> /* for strlen */
#include <strings.h> /* for strcasecmp */
int mycmp(const void *s1, const void *s2)
{
const char *l = *(const char **)s1, *r = *(const char **)s2;
size_t ll = strlen(l), lr = strlen(r);
if (ll > lr) return -1;
if (ll < lr) return 1;
return strcasecmp(l, r);
}
int main()
{
const char *strings[] = {
"Here", "are", "some", "sample", "strings", "to", "be", "sorted" };
qsort(strings, sizeof(strings)/sizeof(*strings), sizeof(*strings), mycmp);
return 0;
}
[edit] C++
#include <algorithm>
#include <string>
#include <cctype>
// compare character case-insensitive
bool icompare_char(char c1, char c2)
{
return std::toupper(c1) < std::toupper(c2);
}
// return true if s1 comes before s2
bool compare(std::string const& s1, std::string const& s2)
{
if (s1.length() > s2.length())
return true;
if (s1.length() < s2.length())
return false;
return std::lexicographical_compare(s1.begin(), s1.end(),
s2.begin(), s2.end(),
icompare_char);
}
int main()
{
std::string strings[8] = {"Here", "are", "some", "sample", "strings", "to", "be", "sorted"};
std::sort(strings, strings+8, compare);
return 0;
}
[edit] C#
C# allows you to specify a custom compare to the built in sort method on a list
using System;
using System.Collections.Generic;
namespace RosettaCode {
class SortCustomComparator {
// Driver program
public void CustomSort() {
String[] items = { "Here", "are", "some", "sample", "strings", "to", "be", "sorted" };
List<String> list = new List<string>(items);
DisplayList("Unsorted", list);
list.Sort(CustomCompare);
DisplayList("Descending Length", list);
list.Sort();
DisplayList("Ascending order", list);
}
// Custom compare
public int CustomCompare(String x, String y) {
int result = -x.Length.CompareTo(y.Length);
if (result == 0) {
result = x.ToLower().CompareTo(y.ToLower());
}
return result;
}
// Output routine
public void DisplayList(String header, List<String> theList) {
Console.WriteLine(header);
Console.WriteLine("".PadLeft(header.Length, '*'));
foreach (String str in theList) {
Console.WriteLine(str);
}
Console.WriteLine();
}
}
}
[edit] Output File
Unsorted ******** Here are some sample strings to be sorted Descending Length ***************** strings sample sorted Here some are be to Ascending order *************** are be Here sample some sorted strings to
[edit] Alternative using Linq (.NET 3.5)
using System;
using System.Collections.Generic;
using System.Linq;
namespace RosettaCode
{
class SortCustomComparator
{
// Driver program
public void CustomSort()
{
List<string> list = new List<string> { "Here", "are", "some", "sample", "strings", "to", "be", "sorted" };
DisplayList("Unsorted", list);
var descOrdered = from l in list
orderby l.Length descending
select l;
DisplayList("Descending Length", descOrdered);
var ascOrdered = from l in list
orderby l
select l;
DisplayList("Ascending order", ascOrdered);
}
// Output routine
public void DisplayList(String header, IEnumerable<string> theList)
{
Console.WriteLine(header);
Console.WriteLine("".PadLeft(header.Length, '*'));
foreach (String str in theList)
{
Console.WriteLine(str);
}
Console.WriteLine();
}
}
}
[edit] 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"]
[edit] Clojure
Clojure's sort function has a 2-argument version where the first argument is a java.util.Comparator, and the second is the collection to be sorted. Thus the heart of this version is a comparator function that satisfies the problem spec. What makes this work is that all Clojure functions (thus rosetta-code defined here) implement the java.util.Comparator interface.
(defn rosetta-compare [s1 s2]
(let [len1 (count s1), len2 (count s2)]
(if (= len1 len2)
(compare (.toLowerCase s1) (.toLowerCase s2))
(- len2 len1))))
(println
(sort rosetta-compare
["Here" "are" "some" "sample" "strings" "to" "be" "sorted"]))
Output:
(strings sample sorted Here some are be to)
An alternative, using sort-by:
(sort-by (juxt (comp - count) #(.toLowerCase %))
["Here" "are" "some" "sample" "strings" "to" "be" "sorted"])
[edit] Common Lisp
In Common Lisp, the sort function takes a "less than" predicate that is used as the comparator. This parameter can be any two-argument function. Note: Common Lisp's sort function is destructive; for lists you should not use the original list afterwards, you should only use the return value.
For example, to sort strings case-insensitively in ascending order:
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")
You can also provide an optional key function which maps each element to a key. The keys are then compared using the comparator. For example, to sort strings by length in descending order:
CL-USER> (defvar *strings*
'("Cat" "apple" "Adam" "zero" "Xmas" "quit" "Level" "add" "Actor" "base" "butter"))
*STRINGS*
CL-USER> (sort *strings* #'> :key #'length)
("butter" "apple" "Level" "Actor" "Adam" "zero" "Xmas" "quit" "base"
"Cat" "add")
[edit] D
import std.stdio, std.string, std.algorithm, std.typecons;
void main() {
"here are Some sample strings to be sorted"
.split
.schwartzSort!q{ tuple(-a.length, a.toUpper) }
.writeln;
}
- Output:
["strings", "sample", "sorted", "here", "Some", "are", "be", "to"]
[edit] Delphi
program SortWithCustomComparator;
{$APPTYPE CONSOLE}
uses SysUtils, Types, Generics.Collections, Generics.Defaults;
var
lArray: TStringDynArray;
begin
lArray := TStringDynArray.Create('Here', 'are', 'some', 'sample', 'strings', 'to', 'be', 'sorted');
TArray.Sort<string>(lArray , TDelegatedComparer<string>.Construct(
function(const Left, Right: string): Integer
begin
Result := Length(Right) - Length(Left);
end));
end.
[edit] E
/** returns a if it is nonzero, otherwise b() */
def nonzeroOr(a, b) { return if (a.isZero()) { b() } else { a } }
["Here", "are", "some", "sample", "strings", "to", "be", "sorted"] \
.sort(fn a, b {
nonzeroOr(b.size().op__cmp(a.size()),
fn { a.compareToIgnoreCase(b) })
})
[edit] Euphoria
include sort.e
include wildcard.e
include misc.e
function my_compare(sequence a, sequence b)
if length(a)!=length(b) then
return -compare(length(a),length(b))
else
return compare(lower(a),lower(b))
end if
end function
sequence strings
strings = reverse({ "Here", "are", "some", "sample", "strings", "to", "be", "sorted" })
puts(1,"Unsorted:\n")
pretty_print(1,strings,{2})
puts(1,"\n\nSorted:\n")
pretty_print(1,custom_sort(routine_id("my_compare"),strings),{2})
Output:
Unsorted:
{
"sorted",
"be",
"to",
"strings",
"sample",
"some",
"are",
"Here"
}
Sorted:
{
"strings",
"sample",
"sorted",
"Here",
"some",
"are",
"be",
"to"
}
[edit] EGL
program SortExample
function main()
test1 string[] = ["Here", "are", "some", "sample", "strings", "to", "be", "sorted"];
test1.sort(sortFunction);
SysLib.writeStdout("Test 1:");
for(i int from 1 to test1.getSize())
SysLib.writeStdout(test1[i]);
end
test2 string[] = ["Cat", "apple", "Adam", "zero", "Xmas", "quit", "Level", "add", "Actor", "base", "butter"];
test2.sort(sortFunction);
SysLib.writeStdout("Test 2:");
for(i int from 1 to test2.getSize())
SysLib.writeStdout(test2[i]);
end
end
function sortFunction(a any in, b any in) returns (int)
result int = (b as string).length() - (a as string).length();
if (result == 0)
case
when ((a as string).toLowerCase() > (b as string).toLowerCase())
result = 1;
when ((a as string).toLowerCase() < (b as string).toLowerCase())
result = -1;
otherwise
result = 0;
end
end
return result;
end
end
- Output:
Test 1: strings sample sorted Here some are be to Test 2: butter Actor apple Level Adam base quit Xmas zero add Cat
[edit] F#
let myCompare (s1:string) (s2:string) =
match compare s2.Length s1.Length with
| 0 -> compare (s1.ToLower()) (s2.ToLower())
| X -> X
let strings = ["Here"; "are"; "some"; "sample"; "strings"; "to"; "be"; "sorted"]
let sortedStrings = List.sortWith myCompare strings
printfn "%A" sortedStrings
Output:
["strings"; "sample"; "sorted"; "Here"; "some"; "are"; "be"; "to"]
[edit] Factor
: my-compare ( s1 s2 -- <=> )
2dup [ length ] compare invert-comparison
dup +eq+ = [ drop [ >lower ] compare ] [ 2nip ] if ;
{ "this" "is" "a" "set" "of" "strings" "to" "sort" } [ my-compare ] sort
[edit] Fantom
The List's sort method can be customised using a custom comparator. This is a method which returns an Int: -1 for less than, 0 for equal, +1 for greater than.
class Main
{
public static Void main ()
{
// sample strings from Lisp example
strs := ["Cat", "apple", "Adam", "zero", "Xmas", "quit",
"Level", "add", "Actor", "base", "butter"]
sorted := strs.dup // make a copy of original list
sorted.sort |Str a, Str b -> Int| // sort using custom comparator
{
if (b.size == a.size) // if size is same
return a.compareIgnoreCase(b) // then sort in ascending lexicographic order, ignoring case
else
return b.size <=> a.size // else sort in descending size order
}
echo ("Started with : " + strs.join(" "))
echo ("Finished with: " + sorted.join(" "))
}
}
Output:
$ fan comparator-sort.fan Started with : Cat apple Adam zero Xmas quit Level add Actor base butter Finished with: butter Actor apple Level Adam base quit Xmas zero add Cat
[edit] Fortran
Fortran does not have builtin to sort arrays (of numbers or strings), with or without custom comparator; so we need modifying e.g. this code in order to handle strings and to accept a custom comparator.
module sorts_with_custom_comparator
implicit none
contains
subroutine a_sort(a, cc)
character(len=*), dimension(:), intent(inout) :: a
interface
integer function cc(a, b)
character(len=*), intent(in) :: a, b
end function cc
end interface
integer :: i, j, increment
character(len=max(len(a), 10)) :: temp
increment = size(a) / 2
do while ( increment > 0 )
do i = increment+1, size(a)
j = i
temp = a(i)
do while ( j >= increment+1 .and. cc(a(j-increment), temp) > 0)
a(j) = a(j-increment)
j = j - increment
end do
a(j) = temp
end do
if ( increment == 2 ) then
increment = 1
else
increment = increment * 5 / 11
end if
end do
end subroutine a_sort
end module sorts_with_custom_comparator
Then we have to put our custom comparator in a module (to_lower is defined here):
module comparators
implicit none
contains
integer function my_compare(a, b)
character(len=*), intent(in) :: a, b
character(len=max(len(a),len(b))) :: a1, b1
a1 = a
b1 = b
call to_lower(b1)
call to_lower(a1)
if ( len(trim(a)) > len(trim(b)) ) then
my_compare = -1
elseif ( len(trim(a)) == len(trim(b)) ) then
if ( a1 > b1 ) then
my_compare = 1
else
my_compare = -1
end if
else
my_compare = 1
end if
end function my_compare
end module comparators
At the end, we can test these:
program CustomComparator
use comparators
use sorts_with_custom_comparator
implicit none
character(len=100), dimension(8) :: str
integer :: i
str = (/ "this", "is", "an", "array", "of", "strings", "to", "sort" /)
call a_sort(str, my_compare)
do i = 1, size(str)
print *, trim(str(i))
end do
end program CustomComparator
[edit] Go
package main
import (
"fmt"
"sort"
"strings"
)
type sortable []string
func (s sortable) Len() int { return len(s) }
func (s sortable) Swap(i, j int) { s[i], s[j] = s[j], s[i] }
func (s sortable) Less(i, j int) bool {
a, b := s[i], s[j]
if len(a) != len(b) {
return len(a) > len(b)
}
return strings.ToLower(a) < strings.ToLower(b)
}
func main() {
var s sortable = strings.Fields("To tell your name the livelong day To an admiring bog")
fmt.Println(s, "(original)")
sort.Sort(s)
fmt.Println(s, "(sorted)")
}
Output:
[To tell your name the livelong day To an admiring bog] (original) [admiring livelong name tell your bog day the an To To] (sorted)
[edit] Groovy
The "custom comparator" is just a closure attached to the sort method invocation.
def strings = "Here are some sample strings to be sorted".split()
strings.sort { x, y ->
y.length() <=> x.length() ?: x.compareToIgnoreCase(y)
}
println strings
Output:
[strings, sample, sorted, Here, some, are, be, to]
[edit] Haskell
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))
[edit] Icon and Unicon
procedure main() #: demonstrate various ways to sort a list and string
write("Sorting Demo for custom comparator")
L := ["Here", "are", "some", "sample", "strings", "to", "be", "sorted"]
write(" Unsorted Input : ")
every write(" ",image(!L))
shellsort(L,cmptask) # most of the RC sorts will work here
write(" Sorted Output : ")
every write(" ",image(!L))
end
procedure cmptask(a,b) # sort by descending length and ascending lexicographic order for strings of equal length
if (*a > *b) | ((*a = *b) & (map(a) << map(b))) then return b
end
Note(1): This example relies on the supporting procedures 'sortop', and 'demosort' in Bubble Sort.
Note(2): This example can utilize any of the sorting algorithms that share the same base code including: Bubble, Cocktail, Comb, Gnome, and Shell.
Note(3): Using 'map' in the 'cmptask' procedure would not be efficient on large lists.
Sorting Demo for custom comparator
Unsorted Input :
"Here"
"are"
"some"
"sample"
"strings"
"to"
"be"
"sorted"
Sorted Output :
"strings"
"sample"
"sorted"
"Here"
"some"
"are"
"be"
"to"
[edit] J
Case-insensitivity is obtained using lower, a verb taken from Change string case. Standard utilities tolower or toupper may be substituted.
mycmp=: 1 :'/:u'
length_and_lex =: (-@:# ; lower)&>
strings=: 'Here';'are';'some';'sample';'strings';'to';'be';'sorted'
length_and_lex mycmp strings
+-------+------+------+----+----+---+--+--+
|strings|sample|sorted|Here|some|are|be|to|
+-------+------+------+----+----+---+--+--+
[edit] Java
import java.util.Comparator;
import java.util.Arrays;
public class Test {
public static void main(String[] args) {
String[] strings = {"Here", "are", "some", "sample", "strings", "to", "be", "sorted"};
Arrays.sort(strings, new Comparator<String>() {
public int compare(String s1, String s2) {
int c = s2.length() - s1.length();
if (c == 0)
c = s1.compareToIgnoreCase(s2);
return c;
}
});
for (String s: strings)
System.out.print(s + " ");
}
}
Same thing as above
import java.util.Comparator;
import java.util.Arrays;
public class ComparatorTest {
public static void main(String[] args) {
String[] strings = {"Here", "are", "some", "sample", "strings", "to", "be", "sorted"};
Arrays.sort(strings, (s1, s2) -> {
int c = s2.length() - s1.length();
if (c == 0)
c = s1.compareToIgnoreCase(s2);
return c;
});
for (String s: strings)
System.out.print(s + " ");
}
}
[edit] JavaScript
function lengthSorter(a, b) {
var result = b.length - a.length;
if (result == 0)
result = a.localeCompare(b);
return result;
}
var test = ["Here", "are", "some", "sample", "strings", "to", "be", "sorted"];
test.sort(lengthSorter);
alert( test.join(' ') ); // strings sample sorted Here some are be to
[edit] Lua
function pair(a, b) return a[1] < b[1] end
t = {
{2, 5}, {1, 6}, {4, 8}, {3, 2}
}
table.sort(t, pair)
for i, v in ipairs(t) do print(unpack(v)) end
[edit] Mathematica
We define a new function to give true or false if two elements are in order. After that we can simply use the built-in Sort with an ordering function:
StringOrderQ[x_String, y_String] :=
If[StringLength[x] == StringLength[y],
OrderedQ[{x, y}],
StringLength[x] >StringLength[y]
]
words={"on","sunday","sander","sifted","and","sorted","sambaa","for","a","second"};
Sort[words,StringOrderQ]
gives back:
{sambaa,sander,second,sifted,sorted,sunday,and,for,on,a}
[edit] Maxima
strangeorderp(a, b) := slength(a) > slength(b) or (slength(a) = slength(b) and orderlessp(a, b))$
s: tokens("Lorem ipsum dolor sit amet consectetur adipiscing elit Sed non risus Suspendisse\
lectus tortor dignissim sit amet adipiscing nec ultricies sed dolor")$
sort(s, strangeorderp);
["Suspendisse", "consectetur", "adipiscing", "adipiscing", "dignissim", "ultricies",
"lectus", "tortor", "Lorem", "dolor", "dolor", "ipsum", "risus", "amet", "amet",
"elit", "Sed", "nec", "non", "sed", "sit", "sit"]
[edit] MAXScript
fn myCmp str1 str2 =
(
case of
(
(str1.count < str2.count): 1
(str1.count > str2.count): -1
default:(
-- String compare is case sensitive, name compare isn't. Hence...
str1 = str1 as name
str2 = str2 as name
case of
(
(str1 > str2): 1
(str1 < str2): -1
default: 0
)
)
)
)
strList = #("Here", "are", "some", "sample", "strings", "to", "be", "sorted")
qSort strList myCmp
print strList
[edit] NetRexx
/* NetRexx */
options replace format comments java crossref symbols nobinary
-- =============================================================================
class RSortCustomComparator public
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
method main(args = String[]) public static
sample = [String 'Here', 'are', 'some', 'sample', 'strings', 'to', 'be', 'sorted']
say displayArray(sample)
Arrays.sort(sample, LengthComparator())
say displayArray(sample)
return
method displayArray(harry = String[]) constant
disp = ''
loop elmt over harry
disp = disp','elmt
end elmt
return '['disp.substr(2)']' -- trim leading comma
-- =============================================================================
class RSortCustomComparator.LengthComparator implements Comparator
method compare(lft = Object, rgt = Object) public binary returns int
cRes = int
if lft <= String, rgt <= String then do
cRes = (String rgt).length - (String lft).length
if cRes == 0 then cRes = (String lft).compareToIgnoreCase(String rgt)
end
else signal IllegalArgumentException('Arguments must be Strings')
return cRes
Output:
[Here,are,some,sample,strings,to,be,sorted] [strings,sample,sorted,Here,some,are,be,to]
[edit] Nial
sort fork [=[tally first,tally last],up, >= [tally first,tally last]] ['Here', 'are', 'some', 'sample', 'strings', 'to', 'be', 'sorted']
=+-------+------+------+----+----+---+--+--+
=|strings|sample|sorted|Here|some|are|be|to|
=+-------+------+------+----+----+---+--+--+
[edit] Objective-C
Using blocks:
#import <Foundation/Foundation.h>
#define esign(X) (((X)>0)?1:(((X)<0)?-1:0))
int main()
{
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
NSMutableArray *arr =
[NSMutableArray
arrayWithArray: [@"this is a set of strings to sort"
componentsSeparatedByString: @" "]
];
[arr sortUsingComparator: ^NSComparisonResult(id obj1, id obj2){
NSComparisonResult l = esign((int)([obj1 length] - [obj2 length]));
return l ? -l // reverse the ordering
: [obj1 caseInsensitiveCompare: obj2];
}];
for( NSString *str in arr )
{
NSLog(@"%@", str);
}
[pool release];
return EXIT_SUCCESS;
}
#import <Foundation/Foundation.h>
@interface NSString (CustomComp)
- (NSComparisonResult)my_compare: (id)obj;
@end
#define esign(X) (((X)>0)?1:(((X)<0)?-1:0))
@implementation NSString (CustomComp)
- (NSComparisonResult)my_compare: (id)obj
{
NSComparisonResult l = esign((int)([self length] - [obj length]));
return l ? -l // reverse the ordering
: [self caseInsensitiveCompare: obj];
}
@end
int main()
{
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
NSMutableArray *arr =
[NSMutableArray
arrayWithArray: [@"this is a set of strings to sort"
componentsSeparatedByString: @" "]
];
[arr sortUsingSelector: @selector(my_compare:)];
NSEnumerator *iter = [arr objectEnumerator];
NSString *str;
while( (str = [iter nextObject]) != nil )
{
NSLog(@"%@", str);
}
[pool release];
return EXIT_SUCCESS;
}
This example can also be written using sort descriptors:
#import <Foundation/Foundation.h>
int main()
{
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
NSArray *strings = [@"Here are some sample strings to be sorted" componentsSeparatedByString:@" "];
NSSortDescriptor *sd1 = [[NSSortDescriptor alloc] initWithKey:@"length" ascending:NO];
NSSortDescriptor *sd2 = [[NSSortDescriptor alloc] initWithKey:@"lowercaseString" ascending:YES];
NSArray *sortDescriptors = [NSArray arrayWithObjects:sd1, sd2, nil];
[sd1 release];
[sd2 release];
NSArray *sorted = [strings sortedArrayUsingDescriptors:sortDescriptors];
NSLog(@"%@", sorted);
[pool release];
return 0;
}
[edit] OCaml
let mycmp s1 s2 =
if String.length s1 <> String.length s2 then
compare (String.length s2) (String.length s1)
else
String.compare (String.lowercase s1) (String.lowercase s2)
List:
# let strings = ["Here"; "are"; "some"; "sample"; "strings"; "to"; "be"; "sorted"];;
val strings : string list =
["Here"; "are"; "some"; "sample"; "strings"; "to"; "be"; "sorted"]
# List.sort mycmp strings;;
- : string list =
["strings"; "sample"; "sorted"; "Here"; "some"; "are"; "be"; "to"]
Array:
# let strings = [|"Here"; "are"; "some"; "sample"; "strings"; "to"; "be"; "sorted"|];;
val strings : string array =
[|"Here"; "are"; "some"; "sample"; "strings"; "to"; "be"; "sorted"|]
# Array.sort mycmp strings;;
- : unit = ()
# strings;;
- : string array =
[|"strings"; "sample"; "sorted"; "Here"; "some"; "are"; "be"; "to"|]
[edit] Oz
declare
fun {LexicographicLessThan Xs Ys}
for
X in {Map Xs Char.toLower}
Y in {Map Ys Char.toLower}
return:Return
default:{Length Xs}<{Length Ys}
do
if X < Y then {Return true} end
end
end
fun {LessThan Xs Ys}
{Length Xs} > {Length Ys}
orelse
{Length Xs} == {Length Ys} andthen {LexicographicLessThan Xs Ys}
end
Strings = ["Here" "are" "some" "sample" "strings" "to" "be" "sorted"]
in
{ForAll {Sort Strings LessThan} System.showInfo}
[edit] PARI/GP
cmp(a,b)=if(#a<#b,1,if(#a>#b,-1,lex(a,b)));
vecsort(v,cmp)
[edit] Perl
sub mycmp { length $b <=> length $a || lc $a cmp lc $b }
my @strings = ("Here", "are", "some", "sample", "strings", "to", "be", "sorted");
my @sorted = sort mycmp @strings;
Or inline:
my @strings = qw/here are some sample strings to be sorted/;
my @sorted = sort {length $b <=> length $a || lc $a cmp lc $b} @strings
Faster with a Schwartzian transform:
my @strings = qw/here are some sample strings to be sorted/;
my @sorted = map { $_->[0] }
sort { $a->[1] <=> $b->[1] || $a->[2] cmp $b->[2] }
map { [ $_, length, lc ] }
@strings;
[edit] Perl 6
my @strings = <Here are some sample strings to be sorted>;
my @sorted_strings = sort { $^a.chars <=> $^b.chars or $^a.lc cmp $^b.lc }, @strings;
.say for @sorted_strings;
This behavior is triggered by use of an arity 2 sort routine.
If instead the function you feed to sort is of arity 1, it will do the Schwartzian transform for you, automatically sorting numeric fields numerically, and strings fields stringily:
my @sorted_strings = sort -> $x { [ $x.chars, $x.lc ] }, @strings;
[edit] PHP
<?php
function mycmp($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");
?>
[edit] PicoLisp
By default, the sort function in PicoLisp returns an ascending list (of any type). To get a result in descending order, the "greater than" function can be supplied
: (sort '("def" "abc" "ghi") >)
-> ("ghi" "def" "abc")
or simply the result reversed (which is, btw, the most efficient way)
: (flip (sort '("def" "abc" "ghi")))
-> ("ghi" "def" "abc")
[edit] PL/I
Platform: WIN
MRGEPKG: package exports(MERGESORT,MERGE,RMERGE);
DCL (T(4)) CHAR(20) VAR; /* scratch space of length N/2 */
MERGE: PROCEDURE (A,LA,B,LB,C,CMPFN);
DECLARE (A(*),B(*),C(*)) CHAR(*) VAR;
DECLARE (LA,LB) FIXED BIN(31) NONASGN;
DECLARE (I,J,K) FIXED BIN(31);
DECLARE CMPFN ENTRY(
NONASGN CHAR(*) VAR,
NONASGN CHAR(*) VAR)
RETURNS (FIXED bin(31));
I=1; J=1; K=1;
DO WHILE ((I <= LA) & (J <= LB));
IF CMPFN(A(I),B(J)) <= 0 THEN
DO; C(K)=A(I); K=K+1; I=I+1; END;
ELSE
DO; C(K)=B(J); K=K+1; J=J+1; END;
END;
DO WHILE (I <= LA);
C(K)=A(I); I=I+1; K=K+1;
END;
return;
END MERGE;
MERGESORT: PROCEDURE (A,N,CMPFN) RECURSIVE ;
DECLARE (A(*)) CHAR(*) VAR;
DECLARE N FIXED BINARY(31) NONASGN;
DECLARE CMPFN ENTRY(
NONASGN CHAR(*) VAR,
NONASGN CHAR(*) VAR)
RETURNS (FIXED bin(31));
DECLARE (M,I) FIXED BINARY;
DECLARE AMP1(N) CHAR(20) VAR BASED(P);
DECLARE P POINTER;
IF (N=1) THEN RETURN;
M = trunc((N+1)/2);
IF M > 1 THEN CALL MERGESORT(A,M,CMPFN);
P=ADDR(A(M+1));
IF (N-M > 1) THEN CALL MERGESORT(AMP1,N-M,CMPFN);
IF CMPFN(A(M),AMP1(1)) <= 0 THEN RETURN;
DO I=1 to M; T(I)=A(I); END;
CALL MERGE(T,M,AMP1,N-M,A,CMPFN);
END MERGESORT;
RMERGE: PROC OPTIONS(MAIN);
DCL I FIXED BIN(31);
DCL A(8) CHAR(20) VAR INIT("this","is","a","set","of","strings","to","sort");
MyCMP: PROCEDURE(A,B) RETURNS (FIXED BIN(31));
DCL (A,B) CHAR(*) VAR NONASGN;
DCL (I,J) FIXED BIN(31);
I = length(trim(A)); J = length(trim(B));
IF I < J THEN RETURN(+1);
IF I > J THEN RETURN(-1);
IF lowercase(A) < lowercase(B) THEN RETURN(-1);
IF lowercase(A) > lowercase(B) THEN RETURN(+1);
RETURN (0);
END MyCMP;
CALL MERGESORT(A,8,MyCMP);
DO I=1 TO 8;
put edit (I,A(I)) (F(5),X(2),A(10)) skip;
END;
put skip;
END RMERGE;
[edit] 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;
NOTE: The definition of compare can also be written thus:
define compare(s1, s2);
lvars
l1 = length(s1),
l2 = length(s2);
l1 > l2 or (l1 == l2 and alphabefore(uppertolower(s1), uppertolower(s2)))
enddefine;
[edit] PowerBASIC
FUNCTION Sorter(p1 AS STRING, p2 AS STRING) AS LONG
'if p1 should be first, returns -1
'if p2 should be first, returns 1
' if they're equal, returns 0
IF LEN(p1) > LEN(p2) THEN
FUNCTION = -1
ELSEIF LEN(p2) > LEN(p1) THEN
FUNCTION = 1
ELSEIF UCASE$(p1) > UCASE$(p2) THEN
'if we get here, they're of equal length,
'so now we're doing a "normal" string comparison
FUNCTION = -1
ELSEIF UCASE$(p2) > UCASE$(p1) THEN
FUNCTION = 1
ELSE
FUNCTION = 0
END IF
END FUNCTION
FUNCTION PBMAIN()
DIM x(7) AS STRING
ARRAY ASSIGN x() = "Here", "are", "some", "sample", "strings", "to", "be", "sorted"
'pb's built-in sorting; "USING" tells it to use our custom comparator
ARRAY SORT x(), USING Sorter()
END FUNCTION
[edit] PowerShell
The Sort-Object cmdlet accepts script blocks as arguments as well as multiple criteria after which to sort.
$list = "Here", "are", "some", "sample", "strings", "to", "be", "sorted"
$list | Sort-Object {-$_.Length},{$_}
The negated string length is the first sort criterion, the second is the string itself, resulting in descending length and ascending lexicographic order.
[edit] Prolog
Works with SWI-Prolog.
rosetta_sort :-
L = ["Here", "are", "some", "sample", "strings", "to", "be", "sorted" ],
predsort(my_comp, L, L1),
writeln('Input list :'),
maplist(my_write, L), nl,nl,
writeln('Sorted list :'),
maplist(my_write, L1).
my_comp(Comp, W1, W2) :-
length(W1,L1),
length(W2, L2),
( L1 < L2 -> Comp = '>'
; L1 > L2 -> Comp = '<'
; compare(Comp, W1, W2)).
my_write(W) :-
format('~s ', [W]).
Output :
?- rosetta_sort. Input list : Here are some sample strings to be sorted Sorted list : strings sample sorted Here some are be to true.
[edit] Python
Using a key function is usually more efficient than a comparator. We can take advantage of the fact that tuples are ordered first by the first element, then by the second, etc., to perform a sort on multiple criteria.
strings = "here are Some sample strings to be sorted".split()
def mykey(x):
return -len(x), x.upper()
print sorted(strings, key=mykey)
Sample output:
['strings', 'sample', 'sorted', 'here', 'Some', 'are', 'be', 'to']
[edit] Alternative method using cmp
To technically comply with this task, we can also use an actual comparator (cmp) function which will be called every time members of the original list are to be compared. Note that this feature is worse than using the key argument and has been removed from Python 3, so should no longer be used in new code.
def mycmp(s1, s2):
return cmp(len(s2), len(s1)) or cmp(s1.upper(), s2.upper())
print sorted(strings, cmp=mycmp)
[edit] Racket
#lang racket
;; Using a combination of the two comparisons
(define (sort1 words)
(sort words (λ(x y)
(define xl (string-length x)) (define yl (string-length y))
(or (> xl yl) (and (= xl yl) (string-ci<? x y))))))
(sort1 '("Some" "pile" "of" "words"))
;; -> '("words" "pile" "Some" "of")
;; Doing two sorts, relying on `sort's stability
(define (sort2 words)
(sort (sort words string-ci<?) > #:key string-length))
(sort2 '("Some" "pile" "of" "words"))
;; -> '("words" "pile" "Some" "of")
[edit] Ruby
Since Ruby 1.8.6 Enumerables have a "sort_by" method, taking a key block, which is more efficient than a comparator. We can take advantage of the fact that Arrays are ordered first by the first element, then by the second, etc., to perform a sort on multiple criteria.
words = %w(Here are some sample strings to be sorted)
p words.sort_by {|word| [-word.size, word.downcase]}
To technically comply with this task, we can also use an actual comparator block which will be called every time members of the original list are to be compared.
p words.sort {|a, b| d = b.size <=> a.size
d != 0 ? d : a.upcase <=> b.upcase}
[edit] Sather
class MAIN is
custom_comp(a, b:STR):BOOL is
l ::= a.length - b.length;
if l = 0 then return a.lower < b.lower; end;
return l > 0;
end;
main is
s:ARRAY{STR} := |"this", "is", "an", "array", "of", "strings", "to", "sort"|;
s.insertion_sort_by(bind(custom_comp(_,_)));
loop #OUT + s.elt! + "\n"; end;
end;
end;
[edit] Scala
List("Here", "are", "some", "sample", "strings", "to", "be", "sorted").sortWith{(a,b) =>
val cmp=a.size-b.size
(if (cmp==0) -a.compareTo(b) else cmp) > 0
}
- Output:
List(strings, sample, sorted, Here, some, are, be, to)
[edit] Scheme
(use srfi-13);;Syntax for module inclusion depends on implementation,
;;as does the presence of a sort function.
(define (mypred? a b)
(let ((len-a (string-length a))
(len-b (string-length b)))
(if (= len-a len-b)
(string>? (string-downcase b) (string-downcase a))
(> len-a len-b))))
(sort '("sorted" "here" "strings" "sample" "Some" "are" "be" "to") mypred?)
Sample output:
("strings" "sample" "sorted" "here" "Some" "are" "be" "to")
[edit] Slate
define: #words -> #('here' 'are' 'some' 'sample' 'strings' 'to' 'sort' 'since' 'this' 'exercise' 'is' 'not' 'really' 'all' 'that' 'dumb' '(sorry)').
words sortBy: [| :first :second | (first lexicographicallyCompare: second) isNegative]
[edit] Smalltalk
#('here' 'are' 'some' 'sample' 'strings' 'to' 'sort' 'since' 'this' 'exercise' 'is' 'not' 'really' 'all' 'that' 'dumb' '(sorry)' ) asSortedCollection
sortBlock:
[:first :second | (second size = first size)
ifFalse: [second size < first size]
ifTrue: [first < second]]
[edit] Standard ML
List:
fun mygt (s1, s2) =
if size s1 <> size s2 then
size s2 > size s1
else
String.map Char.toLower s1 > String.map Char.toLower s2
- val strings = ["Here", "are", "some", "sample", "strings", "to", "be", "sorted"];
val strings = ["Here","are","some","sample","strings","to","be","sorted"]
: string list
- ListMergeSort.sort mygt strings;
val it = ["strings","sample","sorted","Here","some","are","be","to"]
: string list
Array:
fun mycmp (s1, s2) =
if size s1 <> size s2 then
Int.compare (size s2, size s1)
else
String.compare (String.map Char.toLower s1, String.map Char.toLower s2)
- val strings = Array.fromList ["Here", "are", "some", "sample", "strings", "to", "be", "sorted"];
val strings = [|"Here","are","some","sample","strings","to","be","sorted"|]
: string array
- ArrayQSort.sort mycmp strings;
val it = () : unit
- strings;
val it = [|"strings","sample","sorted","Here","some","are","be","to"|]
: string array
[edit] Tcl
proc sorter {a b} {
set la [string length $a]
set lb [string length $b]
if {$la < $lb} {
return 1
} elseif {$la > $lb} {
return -1
}
return [string compare [string tolower $a] [string tolower $b]]
}
set strings {here are Some sample strings to be sorted}
lsort -command sorter $strings ;# ==> strings sample sorted here Some are be to
[edit] TUSCRIPT
$$ MODE TUSCRIPT
setofstrings="this is a set of strings to sort This Is A Set Of Strings To Sort"
unsorted=SPLIT (setofstrings,": :")
PRINT "1. setofstrings unsorted"
index=""
LOOP l=unsorted
PRINT l
length=LENGTH (l),index=APPEND(index,length)
ENDLOOP
index =DIGIT_INDEX (index)
sorted=INDEX_SORT (unsorted,index)
PRINT "2. setofstrings sorted"
*{sorted}
Output:
1. setofstrings unsorted this is a set of strings to sort This Is A Set Of Strings To Sort 2. setofstrings sorted a A is of to Is Of To set Set this sort This Sort strings Strings
[edit] Ursala
A standard library function, psort, takes a list of binary relational predicates and returns a function that uses them in order of decreasing priority to perform a sort. The less or equal length predicate (leql) and lexically less or equal predicate (lleq) are also standard library functions. This task is therefore easily dispatched as shown.
#import std
#show+
data = <'this','is','a','list','of','strings','to','be','sorted'>
example = psort<not leql,lleq+ ~* ~&K31K30piK26 letters> data
The lleq library function is case sensitive, so it is composed with a function to convert the words to lower case on the fly (without destructively modifying them) in order to meet the task requirement of case insensitivity.
output:
strings sorted list this be is of to a
[edit] Visual Basic .NET
Imports System
Module Sorting_Using_a_Custom_Comparator
Function CustomComparator(ByVal x As String, ByVal y As String) As Integer
Dim result As Integer
result = y.Length - x.Length
If result = 0 Then
result = String.Compare(x, y, True)
End If
Return result
End Function
Sub Main()
Dim strings As String() = {"test", "Zoom", "strings", "a"}
Array.Sort(strings, New Comparison(Of String)(AddressOf CustomComparator))
End Sub
End Module
Categories:
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