入力された文から繰り返し単語をすべて削除します。

入力は次のようにcat dog cat dog bird dog Snake snake Snakeなり、出力はになりますcat dog bird Snake snake。単語を区切るスペースは常に1つです。

出力順序は入力と同じでなければなりません。（例を参照）

句読点を処理する必要はありませんが、大文字の処理が必要です。

gs2、3バイト

,É-

CP437でエンコードされています。

STDINは、プログラムの開始時にプッシュされます。,スペースに分割します。Éはuniq、重複をフィルタリングします。-スペースで結合します。

CJam、7文字

qS/_&S*

おそらくはるかに短くすることができます...しかし、私がCJamを使用したことはほとんどありません。^。^

q入力を読み取り、S/スペースで分割し、_&複製し、セットワイズANDを適用して（したがって、重複を取り除きます）、S*スペースで再結合します。

オンライン通訳リンク

Haskell、34バイト

import Data.List
unwords.nub.words

使用例：(unwords.nub.words) "cat dog cat dog bird dog Snake snake Snake"-> "cat dog bird Snake snake"。

APL、22 20バイト

{1↓∊∪(∊∘' '⊂⊢)' ',⍵}

これにより、右側の文字列を受け入れて文字列を返す名前のないモナド関数が作成されます。

説明：

               ' ',⍵}    ⍝ Prepend a space to the input string
     (∊∘' '⊂⊢)          ⍝ Split the string on spaces using a fork
    ∪                    ⍝ Select the unique elements
{1↓∊                     ⍝ Join into a string and drop the leading space

オンラインで試す

デニスのおかげで2バイト節約できました！

ルビー、21文字

->s{s.split.uniq*' '}

JavaScript（ES6）33

（この回答を参照）

EcmaScript 6準拠のブラウザーで以下のスニペットを実行してテストします（セット、スプレッド演算子、テンプレート文字列、矢印関数を実装しています-私はFirefoxを使用しています）。

注：Setへの変換はすべての重複をドロップし、Setは元の順序を維持します。

f=s=>[...Set(s.split` `)].join` `

function test() { O.innerHTML=f(I.value) }

test()

#I { width: 70% }

<input id=I value="cat dog cat dog bird dog Snake snake Snake"/><button onclick="test()">-></button>
<pre id=O></pre>

TeaScript、12バイト

TeaScriptはゴルフ用のJavaScriptです。

xs` `u()j` `

This is pretty short. It splits on each space, filters out duplicates, then rejoins.

Try it online

PowerShell, 15 Bytes

$args|select -u

Whoa, an actual entry where PowerShell is somewhat competitive? That's unpossible!

Takes the string as input arguments, pipes to Select-Object with the -Unique flag. Spits out an array of strings, preserving order and capitalization as requested.

Usage:

PS C:\Tools\Scripts\golfing> .\remove-repeated-words-from-string.ps1 cat dog cat dog bird dog Snake snake Snake
cat
dog
bird
Snake
snake

If this is too "cheaty" in assuming the input can be as command-line arguments, then go for the following, at 24 21 Bytes _{(saved some bytes thanks to blabb)}. Interestingly, using the unary operator in this direction happens to also work if the input string is demarcated with quotes or as individual arguments, since the default -split is by spaces. Bonus.

-split$args|select -u

Julia, 29 bytes

s->join(unique(split(s))," ")

This creates an unnamed function that splits the string into a vector on spaces, keeps only the unique elements (preserving order), and joins the array back into a string with spaces.

R, 22 bytes

cat(unique(scan(,"")))

This reads a string from STDIN and splits it into a vector on spaces using scan(,""), selects only unique elements, then concatenates them into a string and prints it to STDOUT using cat.

Retina, 22 bytes

 (\w+)\b(?<=\b\1\b.+)

Save the file with a trailing linefeed and run it with the -s flag.

This is fairly straight forward in that it matches a single word, and the lookbehind checks whether that same word has appeared in the string before. The trailing linefeed causes Retina to work in Replace mode with an empty replacement string, removing all matches.

Mathematica, 43 39 bytes

StringRiffle@*Keys@*Counts@*StringSplit

Pyth - 9 bytes

Well this is why we're all waiting for Pyth5, could have been 5 bytes.

jdoxzN{cz

Try it online here.

C++11, 291 bytes

#include<iostream>
#include<string>
#include<list>
#include<sstream>
#include<algorithm>
using namespace std;main(){string s;getline(cin,s);list<string>m;stringstream b(s);while(getline(b,s,' '))if(find(m.begin(),m.end(),s)==m.end())m.push_back(s);for(auto a:m)cout<<a<<' ';cout<<endl;}

I don't see a whole lot of C++ answers compared to golfing languages, so why not. Note that this uses C++11 features, and so if your compiler is stuck in the dark ages sufficiently old enough, you may need to pass a special compilation switch to make it use the C++11 standard. For g++, it's -std=c++11 (only needed for versions < 5.2). Try it online

K5, 9 bytes

" "/?" "\

FYI, this is a function.

Explanation

     " "\    Split the input on spaces
    ?        Find all the unique elements
" "/         Join them back together

Matlab: 18 Bytes

unique(d,'stable')

where d is d = {'cat','dog','cat','dog','bird','dog','Snake','snake','Snake'}.

The result is 'cat' 'dog' 'bird' 'Snake' 'snake'

Python 3, 55

l=[]
for x in input().split():l+=[x][x in l:]
print(*l)

Yeesh, this is long. Unfortunately, Python's set doesn't keep the order of the elements, so we have to do the work ourselves. We iterate through the input words, keeping a list l of elements that aren't yet in l. Then, we print the contents of l space-separated.

A string version of l would not work if some words are substrings of other words.

C#, 38 bytes

String.Join(" ",s.Split().Distinct());

Perl 6, 14 bytes

As a whole program the only way you would write it is 21 bytes long

say $*IN.words.unique # 21 bytes

As a lambda expression the shortest is 14 bytes

*.words.unique # 14 bytes

say ( *.words.unique ).('cat dog cat dog bird dog Snake snake Snake')

my &foo = *.words.unique;
say foo $*IN;

While the output is a List, if you put it in a stringifying context it will put a space between the elements. If it was a requirement to return a string you could just add a ~ to the front ~*.words.unique.

If snippets were allowed, you could shorten it to 13 bytes by removing the *.

$_ = 'cat dog cat dog bird dog Snake snake Snake';

say .words.unique

Python 3, 87 80 bytes

turns out the full program version is shorter

s=input().split(' ')
print(' '.join(e for i,e in enumerate(s)if e not in s[:i]))

Did it without regex, I am happy

Try it online

Lua, 94 bytes

function c(a)l={}return a:gsub("%S+",function(b)if l[b]then return""else l[b]=true end end)end

awk, 25

BEGIN{RS=ORS=" "}!c[$0]++

Output:

$ printf "cat dog cat dog bird dog Snake snake Snake" | awk 'BEGIN{RS=ORS=" "}!c[$0]++'
cat dog bird Snake snake $ 
$ 

JavaScript, 106 102 100 bytes

function(s){o={};s.split(' ').map(function(w){o[w]=1});a=[];for(w in o)a.push(w);return a.join(' ')}

// way too long for JS :(

Hassium, 91 bytes

func main(){d=[]foreach(w in input().split(' '))if(!(d.contains(w))){d.add(w)print(w+" ")}}

Run online and see expanded here

PHP 64 59 bytes

function r($i){echo join(" ",array_unique(split(" ",$i)));}

AppleScript, 162 bytes

Interestingly, this is almost identical to the non-repeating characters thing.

set x to(display dialog""default answer"")'s text returned's words
set o to""
repeat with i in x
considering case
if not i is in o then set o to o&i&" "
end
end
o

I didn't actually know the considering keyword before this. the more you know...

Burlesque, 6 bytes

blsq ) "cat dog cat dog bird dog Snake snake Snake"wdNBwD
cat dog bird Snake snake

Rather simple: split words, nub (nub = remove duplicates), convert back to words.

Gema, 21 characters

*\S=${$0;$0}@set{$0;}

(Very similar to the unique character solution, as there are no arrays in Gema, so allowing built-in unique functions not helps us much.)

Sample run:

bash-4.3$ gema '*\S=${$0;$0}@set{$0;}' <<< 'cat dog cat dog bird dog Snake snake Snake'
cat dog bird Snake snake 

Scala, 44 47 bytes

(s:String)=>s.split(" ").distinct.mkString(" ")

EDIT: using toSet might not preserve order, so I'm now using distinct // that just cost me 3 bytes :(

PHP, 37 Bytes

Assuming $s is the input string.

print_r(array_flip(explode(' ',$s)));