Code Golf Stack Exchange is a question and answer site for programming puzzle enthusiasts and code golfers. It only takes a minute to sign up.
Sign up to join this community
In the shortest amount of code in any programming language, filter out the duplicate items in an array of which the order is irrelevant.
Here are some test cases:
[1, 2, 2, 3, 1, 2, 4] => [1, 2, 3, 4]
['a', 'a', 'b', 'a', 'c', 'a', 'd'] => ['a', 'b', 'c', 'd']
I also should note that there currently aren't any open questions that meet these exact criteria.
Ù
Alternatively:
ê
∪
Q
U
u
u
▀
╔
â
{
u
}
Ｄ
U
1, 2, 2, 3, 1, 2, 4 are 3,4 since they appear exactly once.
\$\endgroup\$
set
Try it online! It also works on Python 2
Or without set:
lambda l:[*dict(zip(l,l))]
Try it online! Thanks to Jonathan Alan and Surculose Sputum for helping me golf this one!
lambda l:list({e:1for e in l}) saving four
\$\endgroup\$
Mar 21, 2020 at 18:34
lambda l:[*dict(zip(l,l))], making use of splat operator to save 3 bytes
\$\endgroup\$
Mar 21, 2020 at 19:01
S->S.distinct()
Stream I/O.
27 22 bytes:
java.util.HashSet::new
-5 bytes thanks to @OlivierGrégoire.
List input, Set output.
java.util.HashSet::new for the List input, Set output.
\$\endgroup\$
Mar 23, 2020 at 11:04
::.. Thanks!
\$\endgroup\$
Mar 23, 2020 at 11:08
->a{a&a}
or
->a{a|a}
Set intersection (&) or set union (|), both of which remove duplicates. Shorter than the built-in uniq method.
D`
G`.
Try it online! Doesn't work on empty strings. Explanation:
D`
Replace all duplicates with empty strings.
G`.
Remove all empty strings.
a=>new Set(a)
Unfortunately Set must be used with new, otherwise the answer will be just 3 bytes: Set, as a function.
@Echo Off&Setlocal EnableDelayedExpansion
For %%A In (%~1)do (
Set M=F
IF "!O!"=="" (Set O=%%A) Else (
For %%B in (!O!)do If %%A==%%B Set M=T
IF !M!==F Set O=!O!,%%A))
ECHO(!O!
Builds a string starting with first element of the original string, compares each element of the new string against the next element of the original string, assigning and testing a troothy value before appending the next element to the new string.
Ｗ⁻θυ⊞υ⊟ιυ
Try it online! Link is to verbose version of code. Works best on strings due to the way Charcoal prints numbers by default. Explanation:
Ｗ⁻θυ
Remove all occurrences of elements in the result from the input. While this temporary value is not empty...
⊞υ⊟ι
... push the last element of that value to the result.
υ
Print the result.
f(a:b)=a:f[x|x<-b,x/=a]
f x=x
This answer gives us the list with the first occurrence of every element.
f(a:b)=[a|notElem a b]++f b
f x=x
This answer gives us the last occurrence of every element.
import Data.List;nub do the same at 20 bytes?
\$\endgroup\$
Mar 21, 2020 at 14:03
Great thanks for the Haskell answer! (so that I can port it)
u([H|T])->[H]++u([X||X<-T,X/=H]);u(I)->I.
It's a recursive definition of uniquifying. The premise is that Erlang doesn't have a set-conversion built-in.
u([H|T])->case string:find(T,[H])of nomatch->[H];_->[]end++u(T);u(I)->I.
u([H|T])-> % Try to split the input into a head & tail.
case string:find(T,[H])of
% Check whether H is a substring of T.
% Strings are lists in Erlang, so it
% doesn't raise a type error when applied on lists.
nomatch->[H];
% If false, return head.
_->[]end % Else, return empty list.
++u(T); % Recurse down until ...
u(I) % ... the operand is an empty list,
->I. % where the operand is returned
```
@_{<>}=0;say for keys%_
Reads an array from STDIN, one element per line. Writes the unique elements to STDOUT, elements separated by two newlines.
(No TIO link, as it seems to not terminate the final line of the input with a newline, which leads to an incorrect output).
say for uniq@ARGV
Accepts an array as arguments, prints the unique elements to STDOUT, one element per line.
TIO
@Unique(i)
Takes input from multi-value field i. Screenshots below.
DeleteDuplicates without the function declaration m:=.
\$\endgroup\$
return #372:remove_duplicates(@args)
Extremely implementation-specific. The shortest non-implementation-specific way of doing this is return $list_utils:remove_duplicates(@args) (43 bytes).
Unfortunately, functions aren't first-class objects in this language, so #372:remove_duplicates (22 bytes) is a syntax error and thus isn't valid.
The shortest way of doing this without using a builtin is x={};for y in (args[1])x=setadd(x,y);endfor return x; (53 bytes)
SELECT DISTINCT v FROM t
Takes input as separate rows in a table t with varchar field v, which is permitted per our IO rules.
Without an ORDER BY, SQL returns the rows in a non-prescribed order.
#import<set>
using s=std::set<int>;s f(int*a,int l){return s{a,a+l};}
This is what I like about C++: It has a lot of features.
i,j;f(a,l)int*a;{for(i=l;i--;)for(j=l;j--;)i-j?a[i]-a[j]?:bcopy(a-~i,a+i,--l-i<<2):0;}
Hoping to roll the two loops together.
i,j;f(a,l)int*a;{for(i=j=l;i-=j--==l;j=j?:l)i-j?a[i]-a[j]?:bcopy(a-~i,a+i,--l-i<<2):0;}
Turns out longer.
sort -u
sort|uniq
bash because it doesn't provide plain sh, but it should work fine in any shell.sh doesn't have arrays. If you wanted to do it with, e.g., bash arrays, you could do this (TIO):a=(1 2 2 3 1 2 4 a a b a c a d)
printf '%s\n' "${a[@]}" | sort -u
[1, 2] => [2, 1]being valid. I'd also suggest tweaking the title to something that doesn't imply order preservation. Perhaps involving the phrase "set of unique items" \$\endgroup\$