Remove duplicate elements: Difference between revisions
(There is only one example, no need for two pieces of code) |
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unique = list(set(items)) |
unique = list(set(items)) |
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See also http://www.peterbe.com/plog/uniqifiers-benchmark and http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/52560 |
See also http://www.peterbe.com/plog/uniqifiers-benchmark and http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/52560 |
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==[[Raven]]== |
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[[Category:Raven]] |
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[ 1 2 3 'a' 'b' 'c' 2 3 4 'b' 'c' 'd' ] as items |
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items copy unique print |
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list (8 items) |
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0 => 1 |
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1 => 2 |
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2 => 3 |
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3 => "a" |
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4 => "b" |
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5 => "c" |
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6 => 4 |
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7 => "d" |
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==[[Ruby]]== |
==[[Ruby]]== |
Revision as of 14:08, 6 November 2007
You are encouraged to solve this task according to the task description, using any language you may know.
Given an Array, derive a data structure containing a sequence of elements, derive a sequence of elements in which all duplicates are removed.
Ada
Compiler: GNAT-gpl 2007
with Ada.Containers.Ordered_Sets; with Ada.Text_IO; use Ada.Text_IO; procedure Unique_Set is package Int_Sets is new Ada.Containers.Ordered_Sets(Integer); use Int_Sets; Nums : array (Natural range <>) of Integer := (1,2,3,4,5,5,6,7,1); Unique : Set; Set_Cur : Cursor; Success : Boolean; begin for I in Nums'range loop Unique.Insert(Nums(I), Set_Cur, Success); end loop; Set_Cur := Unique.First; loop Put_Line(Item => Integer'Image(Element(Set_Cur))); exit when Set_Cur = Unique.Last; Set_Cur := Next(Set_Cur); end loop; end Unique_Set;
AppleScript
set array to {1, 2, 3, "a", "b", "c", 2, 3, 4, "b", "c", "d"} set unique to {} repeat with i in array -- very important -- list index starts at 1 not 0 if (i is not in unique) then set unique to unique & i end if end repeat
Objective-C
NSArray *items = [NSArray arrayWithObjects:@"A", @"B", @"C", @"B", @"A", nil]; NSSet *unique = [NSSet setWithArray:items];
C++
#include <set> #include <iostream> using namespace std; int main( int argc, char* argv[] ) { typedef set<int> TyHash; int data[] = {1, 2, 3, 2, 3, 4}; TyHash hash(data, data + 6); cout << "Set items:" << endl; for (TyHash::iterator iter = hash.begin(); iter != hash.end(); iter++) cout << *iter << " "; cout << endl; }
Alternative method working directly on the array:
#include <iostream> #include <iterator> #include <algorithm> // helper template template<typename T> T* end(T (&array)[size]) { return array+size; } int main() { int data[] = { 1, 2, 3, 2, 3, 4 }; std::sort(data, end(data)); int* new_end = std::unique(data, end(data)); std::copy(data, new_end, std::ostream_iterator<int>(std::cout, " "); std::cout << std::endl; }
C#
Compiler: MSVS 2005
List<int> nums = new List<int>( new int { 1, 1, 2, 3, 4, 4 } ); List<int> unique = new List<int>(); foreach( int i in nums ) if( !unique.Contains( i ) ) unique.Add( i );
Common Lisp
To remove duplicates non-destructively:
(remove-duplicates '(1 3 2 9 1 2 3 8 8 1 0 2)) > (9 3 8 1 0 2)
Or, to remove duplicates in-place:
(delete-duplicates '(1 3 2 9 1 2 3 8 8 1 0 2)) > (9 3 8 1 0 2)
D
void main() { int[] data = [1, 2, 3, 2, 3, 4]; int[int] hash; foreach(el; data) hash[el] = 0; }
E
[1,2,3,2,3,4].asSet().getElements()
Erlang
List = [1, 2, 3, 2, 2, 4, 5, 5, 4, 6, 6, 5]. Set = sets:from_list(List).
Forth
Forth has no built-in hashtable facility, so the easiest way to achieve this goal is to take the "uniq" program as an example.
The work uniq, if given a sorted array of cells, will remove the duplicate entries and return the new length of the array. For simplicity, uniq has been written to process cells (which are to Forth what "int" is to C), but could easily be modified to handle a variety of data types through deferred procedures, etc.
The input data is assumed to be sorted.
\ Increments a2 until it no longer points to the same value as a1 \ a3 is the address beyond the data a2 is traversing. : skip-dups ( a1 a2 a3 -- a1 a2+n ) dup rot ?do over @ i @ <> if drop i leave then cell +loop ; \ Compress an array of cells by removing adjacent duplicates \ Returns the new count : uniq ( a n -- n2 ) over >r \ Original addr to return stack cells over + >r \ "to" addr now on return stack, available as r@ dup begin ( write read ) dup r@ < while 2dup @ swap ! \ copy one cell cell+ r@ skip-dups cell 0 d+ \ increment write ptr only repeat r> 2drop r> - cell / ;
Here is another implementation of "uniq" that uses a popular parameters and local variables extension words. It is structurally the same as the above implementation, but uses less overt stack manipulation.
: uniqv { a n \ r e -- n } a n cells+ to e a dup to r \ the write address lives on the stack begin r e < while r @ over ! r cell+ e skip-dups to r cell+ repeat a - cell / ;
To test this code, you can execute:
create test 1 , 2 , 3 , 2 , 6 , 4 , 5 , 3 , 6 , here test - cell / constant ntest : .test ( n -- ) 0 ?do test i cells + ? loop ; test ntest 2dup cell-sort uniq .test
output
1 2 3 4 5 6 ok
Haskell
values = [1,2,3,2,3,4] unique = List.nub values
IDL
result = uniq( array[sort( array )] )
Java
//Using Java 1.5/5.0 Object[] data = new Object[] {1, 2, 3, "a", "b", "c", 2, 3, 4, "b", "c", "d"}; Set uniqueSet = new HashSet(Arrays.asList(data)); Object[] unique = uniqueSet.toArray();
MAXScript
uniques = #(1, 2, 3, "a", "b", "c", 2, 3, 4, "b", "c", "d") for i in uniques.count to 1 by -1 do ( id = findItem uniques uniques[i] if (id != i) do deleteItem uniques i )
Perl
Interpreter: Perl
use List::MoreUtils qw(uniq); my @uniq = uniq qw(1 2 3 a b c 2 3 4 b c d);
Without modules:
my %seen; my @uniq = grep {!$seen{$_}++} qw(1 2 3 a b c 2 3 4 b c d);
PHP
$list = array(1, 2, 3, 'a', 'b', 'c', 2, 3, 4, 'b', 'c', 'd'); $unique_list = array_unique($list);
Pop11
;;; Initial array lvars ar = {1 2 3 2 3 4}; ;;; Create a hash table lvars ht= newmapping([], 50, 0, true); ;;; Put all array as keys into the hash table lvars i; for i from 1 to length(ar) do 1 -> ht(ar(i)) endfor;
;;; Collect keys into a list lvars ls = []; appdata(ht, procedure(x); cons(front(x), ls) -> ls; endprocedure);
Prolog
uniq(Data,Uniques) :- sort(Data,Uniques).
Example usage:
?- uniq([1, 2, 3, 2, 3, 4],Xs). Xs = [1, 2, 3, 4]
Python
items = [1, 2, 3, 'a', 'b', 'c', 2, 3, 4, 'b', 'c', 'd'] unique = list(set(items))
See also http://www.peterbe.com/plog/uniqifiers-benchmark and http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/52560
Raven
[ 1 2 3 'a' 'b' 'c' 2 3 4 'b' 'c' 'd' ] as items items copy unique print
list (8 items) 0 => 1 1 => 2 2 => 3 3 => "a" 4 => "b" 5 => "c" 6 => 4 7 => "d"
Ruby
ary = [1,1,2,1,'redundant',[1,2,3],[1,2,3],'redundant'] uniq_ary = ary.uniq # => [1, 2, "redundant", [1, 2, 3]]
Scala
val list = List(1,2,3,4,2,3,4,99) val l2 = list.removeDuplicates // l2: scala.List[scala.Int] = List(1,2,3,4,99)
Tcl
The concept of an "array" in TCL is strictly associative - and since there cannot be duplicate keys, there cannot be a redundant element in an array. What is called "array" in many other languages is probably better represented by the "list" in TCL (as in LISP).
set result [lsort -unique $listname]