Split string on first occurrence of each character

Question

Related.

Given a printable ASCII string, split it into a list of non-empty strings with a new sub-string beginning every time a character, which has not previously been seen in the same case, occurs.

Examples

"mississippi" → ["m","i","ssissi","ppi"]

"P P & C G" → ["P"," P ","& ","C ","G"]

"AAA" → ["AAA"]

"Adam" → ["A","d","a","m"]

"" → []

---

^{Anecdote: The result will have between 0 and 95 elements. The 95th sub-string will necessarily continue until the end because at that point, all printable ASCII characters have begun a sub-string, so every additional character will have occurred before and thus cannot cause a new sub-string to begin.}

Answer 1

Red, 79 bytes

func[s][foreach c next unique/case append s"^@"[print copy/part s s: find s c]]

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Ungolfed:

f: func [s] [
    b: next unique/case append s "^@"  ; append `null` to the end of the string, than
                                       ; find the unique characters and 
                                       ; store all except the first to b  
    foreach c b [                      ; for each character in b
        print copy/part s s: find s c  ; print the part of the string to
                                       ; where the character is found and
                                       ; set the beginning of the string to that position
    ]
] 

Answer 2

Retina 0.8.2, 22 20 19 bytes

1>`(.)(?<!\1.+)
¶$&

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Answer 3

GNU sed, 37 bytes

(includes +1 for -r option)

s/./\n&/g
:a
s/((.).*)\n\2/\1\2/
ta

We start by prepending a newline to every character in the string; then in the loop, we remove those that precede a second or subsequent occurrence.

Note that newline can't occur in the input, as that's the separator between strings. And it's not classified as a printable character.

Answer 4

SNOBOL4 (CSNOBOL4), 115 91 77 bytes

	N =INPUT
S	N LEN(1) . Y	:F(END)
	S =S Y
	N SPAN(S) . OUTPUT REM . N	:(S)
END

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Prints the substrings separated by newlines.

Explanation:

line S (for SPLIT) doesn't actually split, but instead extracts the first character of N and saves it (.) to Y. On Failure, it jumps to END. The match should only fail when N is the empty string. Thus, when the input is empty, it jumps directly to END and outputs nothing.

S = S Y concatenates Y onto S.

SPAN(S) greedily matches a run of characters in S, and sends it (.) to OUTPUT, setting (.) N to the REMaining characters of N (if there are any). Then it jumps back to S.

Answer 5

PowerShell, 73 bytes

{$r=@();$h=@{};[char[]]$ARGS[0]|%{if(!($h[$_]++)){$r+=""};$r[-1]+=$_};$r}

Usage

PS> & {$r=@();$h=@{};[char[]]$ARGS[0]|%{if(!($h[$_]++)){$r+=""};$r[-1]+=$_};$r} "mississipi" | ConvertTo-Json -Compress
["m","i","ssissi","pi"]

Answer 6

Ruby, 65 62 58 bytes

->s,*a{s.size.times{|i|(i==s.index(c=s[i])?a:a[-1])<<c}
a}

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A lambda accepting a string and returning an array of strings.

Approach: For each index, either append the character at that index in s to the result array, or to the last string in the result array. String#index returns the index of the first instance of the argument.

-2 bytes: Initialize a as a splat argument instead of on its own line. Thanks, Value Ink!

-1 byte: Use c=s[i]...c instead of s[i]...s[i]. Thanks, Value Ink!

-4 bytes: Use .times instead of .map

Answer 7

Gema, 20 characters

?=${$1;\n}@set{$1;}?

Sample run:

bash-4.4$ gema '?=${$1;\n}@set{$1;}?' <<< 'mississippi'

m
i
ssissi
ppi

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Answer 8

Ruby, 40 bytes

->a{i=0
a.slice_when{a.index(_2)==i+=1}}

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Answer 9

Uiua ^SBCS, 6 bytes

⊜□\+◰.

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⊜□\+◰.
     .  # duplicate
    ◰   # mark firsts
  \+    # cumulative sum
⊜□      # split

Answer 10

APL (Dyalog APL), 3 bytes

≠⊂⊢

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≠ the Boolean mask indicating first occurrence of each character…

⊂ splits…

⊢ the argument

Answer 11

Vyxal, 5 bytes

ÞUÞṗḢ

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  Þṗ  # Partition before
ÞU    # Uniquity mask
    Ḣ # Remove leading empty list

Answer 12

Scala 3, 109 bytes

_.foldLeft(Seq.empty)((l,c)=>if(l.exists(_.contains(c)))l.dropRight(1):+l.last.appended(c)else l:+c.toString)

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Answer 13

Arturo, 42 bytes

$=>[0s:[]chunk&'c[if¬in? c,s->+1's++c<=]]

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Answer 14

Javascript, 200 bytes

My first (I think?) attempt at code golf:

function split(s) {let x=[];let y=[];let z="";let w=1;for(l of s.split('')){if (x.includes(l)){z+=l;}else{w=!w;if (w) {y.push(z);z='';w=0;}z+=l;x.push(l);}}y.push(z);if (y.join('')==0) y=[];return y;}

Answer 15

Mathematica, 84 bytes

a@{}={};a@b_:=a@b[[;;(c@b=Position[b,Tally[b][[-1,1]]][[1,1]])-1]]~Append~b[[c@b;;]]

Defines a function a. Takes a list of characters as input and returns a list of lists of characters as output. Uses a basic recursive structure.

Answer 16

Perl 5 + -p, 37 bytes

for$a(32..126){$a=chr$a;s/\Q$a/\n$a/}

Run through printable ASCII and insert a newline before the first appearance

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Answer 17

Lua, 74 bytes

t={}print(((...):gsub(".",load"c=...a=(t[c]or'\\n')..c t[c]=''return a")))

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Prints one additional leading newline.

Answer 18

C++, 176 bytes

#include<string>
#include<set>
std::string*s(std::string e){auto*r=new std::string[96];std::set<int>u;for(char p:e){if(u.find(p)==u.end())u.insert(p);r[u.size()]+=p;}return r;}

Returns an array of strings, valid strings member of the answer array are not of size 0.
Each call of the function allocate sizeof(std::string)*96, with the pointer returned, and must be delete[]d after usage. Code to test :

auto tests = {
    "mississippi","P P & C G", "AAA", "Adam",""
};

for (const auto& a : tests) {

    std::string* res = s(a);

    for (int i = 0; i < 96; ++i) {
        if (res[i].size() > 0)
            std::cout << '\"' << res[i] << "\", ";
    }

    delete[] res;
    std::cout << '\n';
}

Answer 19

AWK, 63 bytes

func u(v){for(;j++<split(v,A,"");)S[s]=S[s+=m[A[j]]++?0:1]A[j]}

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Calling function u() assigns strings to string array S[] which is of size s

TIO link has some functionality in the footer to clear assigned variables.

Might be able to save a byte or two by using FS="", but this is a more general solution.

Answer 20

JavaScript, 105 87 bytes

Changes: replaced poop emojis for tabs (Thanks @Adám !), replaced parenthesis and aposthrophes for template literals

a=[];f=s=>s.split``.map(x=>!a.includes(x)&&a.push(x)?'  '+x:x).join``.split`    `.slice(1);

Takes a string, returns an array of strings. A big chunk is converting from String->[char]->String->[string]. whitout conversions, this becomes:

a=[];f=s=>s.map(x=>!a.includes(x)&&a.push(x)?'\n'+x:x).join``.slice(1);

takes char array, returns newline separated string (71 bytes).

Also, this is my first post on this stack exchange!

Answer 21

PowerShell, 61 bytes

$args|% t*y|%{if(!($r-cmatch"^[$_]")){$r+=,''};$r[-1]+=$_}
$r

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Answer 22

Clojure, 111 96 bytes

#(reverse(reduce(fn[[f & r :as R]i](if((set(apply str R))i)(cons(str f i)r)(cons(str i)R)))[]%))

As Jim Carrey would say: Beautiful! :D

Answer 23

Java 8, 159 bytes

134 bytes of lambda + 25 bytes for HashSet import. Rip all linters and IDEs.

import java.util.HashSet;
...
s->{HashSet h=new HashSet();return s.chars().mapToObj(c->(char)c+"").reduce("",(x,y)->x+(!h.isEmpty()&h.add(y)?","+y:y)).split(",");};

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Answer 24

Japt, 8 bytes

ò@bY ¶°T

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Answer 25

JavaScript (Node.js), 31 bytes

x=>x.match(/.((.)(?<=\2.+))*/g)

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Pure regex