Interleave strings

Question

Inspiration.* I cannot believe we have not had this challenge before:

Task

Given one or more printable ASCII strings, interleave them by taking one character from each string, cyclically until out of characters. If a string runs out of characters before the others, just skip that one from then on.

Examples

SIMPLE gives SIMPLE

POLLS and EPEES gives PEOPLELESS

LYES and APRONS gives LAYPERSONS

ABCDE and a c and 123 567 gives Aa1B 2Cc3D E567

"\n$?* and ​ (empty string) and ,(.)" (trailing space) gives ",\(n.$)?"* (trailing space)

---

^{* There are shorter APL solutions.}

Answer 1

Jelly, 1 byte

Z

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The “transpose” built-in will do exactly this to a list of strings.

Answer 2

Python 2, 101 89 86 69 bytes

I'm hoping I can get this into a lambda somehow, shortening it down by making it recursive. It isn't ideal because you would hope transposing is shorter, unfortunately it isn't (from what I have managed to come up with so far).

f=lambda s:' '*any(s)and''.join(x[:1]for x in s)+f([x[1:]for x in s])

Old solutions:

w=input();o=''
while any(w):
 for i in range(len(w)):o+=w[i][:1];w[i]=w[i][1:]
print o

lambda s:''.join(''.join([c,''][c<' ']for c in x)for x in map(None,*[list(y)for y in s]))

w=input();o=''
while any(x>=' 'for x in w):
 for i in range(len(w)):o+=w[i][:1];w[i]=w[i][1:]
print o

^{thanks to mathmandan for making me feel dumb ;) saved me a bunch of bytes! (on an old solution)}

Answer 3

Perl 6, 34 32 bytes

{[~] flat roundrobin |$_».comb}

{roundrobin(|$_».comb).flat.join}

A lambda that takes an array of strings as argument, and returns a string.

(Try it online)

Answer 4

CJam, 4 bytes

qN/z

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We can also write an unnamed function for 4 bytes, which expects a list of strings on top of the stack:

{zs}

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Answer 5

Pyth - 3 bytes

Very simple, will add expansion later, on mobile.

s.T

Test Suite

s                         Join all the strings together
 .T                       Transpose, without chopping off overhang
  (Q implicit)

Answer 6

JavaScript (ES6), 52 46 bytes

f=([[c,...s],...a])=>s+a?c+f(s+s?[...a,s]:a):c

Takes input as an array of strings and outputs as a single string.

Test snippet

f=([[c,...s],...a])=>s+a?c+f(s+s?[...a,s]:a):c

g=a=>console.log("Input:",JSON.stringify(a),"Output:",JSON.stringify(f(a)))

g(["SIMPLE"])
g(["POLLS","EPEES"])
g(["LYES","APRONS"])
g(["ABCDE","a c","123 567"])
g(["\"\\n$?*",",(.)\" "]) // Backslash and quote are escaped, but in/output are correct

Answer 7

Haskell, 33 bytes

import Data.List
concat.transpose

Try it on Ideone. Usage:

Prelude Data.List> concat.transpose$["ABCDE","a c","123 567"]
"Aa1B 2Cc3D E567"

---

Without using a build-in: (38 34 bytes)

f[]=[]
f x=[h|h:_<-x]++f[t|_:t<-x]

Try it on Ideone. 4 bytes off thanks to Zgarb! Usage:

Prelude> f["ABCDE","a c","123 567"]
"Aa1B 2Cc3D E567"

Answer 8

PHP, 68 67 bytes

for(;$f=!$k=$f;$i++)for(;y|$v=$argv[++$k];$f&=""==$c)echo$c=$v[$i];

Loops over command line arguments. Run with -r.

After the inner loop, $f is 1 when all strings are finished, 0 else (bitwise & casts ""==$c to int).
Next iteration of the outer loop: copy $f to $k (saves one byte from $k=0) and toggle $f:
When all strings are done, $f is now false and the loop gets broken.

Answer 9

C, 114 84 bytes

-20 bytes for not calculating the length.

i,b;f(char**s){b=1;while(b){i=-1;b=0;while(s[++i]>0)if(*s[i])putchar(*s[i]++),++b;}}

Accepts array of char pointers and requires last item to be a null-pointer (see usage).

Ungolfed and usage:

i,b;f(char**s){
 b=1;
 while(b){
  i=-1;
  b=0;
  while(s[++i]>0)
   if(*s[i])
    putchar(*s[i]++),++b;
 }
}


int main(){
 char*a[]={ 
//  "POLLS","EPEES"
//  "LYES","APRONS"
 "ABCDE","a c","123 567"
 ,0};
 f(a);
 puts("");
}

Answer 10

Retina, 13 bytes

Byte count assumes ISO 8859-1 encoding.

O$#`.
$.%`
¶

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Explanation

O$#`.
$.%`

This is based on the standard transposition technique in Retina. We sort (O) all non-linefeed characters (.), by ($#) the number of characters in front of them on the same line ($.%`), i.e. their horizontal position.

The second stage then simply removes linefeeds from the input.

Answer 11

Java, 19+155=174 160

String f(java.util.Queue<String> q){String s,r="";while(!q.isEmpty()){s=q.poll();r+=s.isEmpty()?"":s.charAt(0);if(s.length()>1)q.add(s.substring(1));}return r;}

Ungolfed:

  String f(java.util.Queue<String> q) {
    String s, r = "";
    while (!q.isEmpty()) {
      s = q.poll();
      r += s.isEmpty() ? "" : s.charAt(0);
      if (s.length() > 1) {
        q.add(s.substring(1));
      }
    }
    return r;
  }

Output:

SIMPLE

PEOPLELESS

LAYPERSONS

Aa1B 2Cc3D E567

",(n.$)?"* ​

First modification: merged string declaration to save some bytes. Removed import, it was used by the main() method (not shown here) that also needed LinkedList. It is fewer bytes to referece Queue directly.

Answer 12

Actually, 7 6 bytes

Golfing suggestions welcome! Try it online!

Edit: -1 byte thanks to Teal pelican.

a Z♂ΣΣ

Ungolfing

          Implicit input each string.
a         Invert the stack so that the strings are in the correct order.
<space>   Get the number of items on the stack, len(stack).
Z         Zip all len(stack) strings into one, transposing them.
♂Σ        sum() every transposed list of chars into strings.
Σ         sum() again to join the strings together.

Answer 13

PHP, 77 bytes

Golfed

function($a){for($d=1;$d!=$s;$i++){$d=$s;foreach($a as$v)$s.=$v[$i];}echo$s;}

Anonymous function that takes an array of strings.

I'm sure this could be golfed more, but it's early. On each iteration, we grab the i-th letter from each given string and append it to our final string, one at a time. PHP just throws warnings if we access bits of strings that don't exist, so that's fine. We only stop when no changes have been made after looping through all the strings once.

I feel like the usage of $d can be golfed more, but it's early. :P

Answer 14

JavaScript (ES6), 46 bytes

f=([[c,...s],...a])=>c?c+f([...a,s]):a+a&&f(a)

<textarea oninput=o.textContent=f(this.value.split`\n`)></textarea><div id=o>

Answer 15

Python 2, 58 bytes

lambda*m:''.join(map(lambda*r:''.join(filter(None,r)),*m))

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Answer 16

J, 13 bytes

({~/:)&;#\&.>

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Based on the inspiration for this question.

Another way to do it takes 27 bytes but operates using transpose. Most of the bytes are to handle the automatically added zeroes from padding.

[:u:0<:@-.~[:,@|:(1+3&u:)&>

Explanation

({~/:)&;#\&.>  Input: list of boxed strings S
          &.>  For each boxed string x in S
        #\       Get the length of each prefix from shortest to longest
                 This forms the range [1, 2, ..., len(x)]
                 Rebox it
(    )         Operate on S and the prefix lengths
      &;         Raze both
   /:            Grade up the raze of the prefix lengths
 {~              Index into the raze of S using the grades
               Return

Answer 17

Bash + GNU utilities, 55

 eval paste `sed "s/.*/<(fold -1<<<'&')/g"`|tr -d \\n\\t

I/O via STDIN (line-separated) and STDOUT.

The sed formats each line to a bash process substitution. These are then evaled into paste to do the actual interleaving. tr then removes unnecessary newlines and tabs.

Ideone.

Answer 18

PHP, 63 bytes

Note: uses IBM-850 encoding

for(;$s^=1;$i++)for(;n|$w=$argv[++$$i];$s&=$x<~■)echo$x=$w[$i];

Run like this:

php -r 'for(;$s^=1;$i++)for(;n|$w=$argv[++$$i];$s&=$x<~■)echo$x=$w[$i];' "\"\n\$?*" "" ",(.)\" " 2>/dev/null;echo
> ",\(n.$)?"* 

Explanation

for(                       # Iterate over string index.
  ;
  $s ^= 1;                 # Continue until $s (stop iterating) is 1.
                           # Flip $s so each iteration starts with $s
                           # being 1.
  $i++                     # Increment string index.
)
  for(
    ;
    "n" | $w=$argv[++$$i]; # Iterate over all input strings. OR with "n"
                           # to allow for empty strings.
    $s &= $x<~■            # If last character printed was greater than
                           # \x0 (all printable chars), set $s to 0,
                           # causing the loop to continue.
  )
    echo $x = $w[$i];      # Print char $i of current string.

Answer 19

Python 3, 75 Bytes

I know the other Python one is shorter, but this is the first time I've used map ever in my life so I'm pretty proud of it

lambda n:''.join(i[k]for k in range(max(map(len,n)))for i in n if len(i)>k)

Answer 20

C, 75 71 bytes

Only limitation is the output length. Currently it's 99, but can be easily stretched to 999 (+1 byte).

i;main(a,b)char**b;{a--;for(;i<99;i++)*b[i%a+1]&&putchar(*b[i%a+1]++);}

Ungolfed:

i;
main( a, b )
char **b;
{
    a--;
    for( ; i < 99; i++ )
        *b[i % a + 1] && putchar( *b[i % a + 1]++ );
}

Answer 21

Python 2, 128 96

I was hoping not to have to use itertools

a=lambda a:"".join([i for i in reduce(lambda: b,c:b+c, map(None,*map(lambda m:list(m),a)) if i])

Ungolfed

 a=lambda a:                              #Start a lambda taking in a
    "".join(                              #Join the result together with empty string
        [i for i in reduce(               #For every item, apply the function and 'keep'
           lambda: b,c:b+c,               #Add lists from...
                map(None,*map(            #None = Identity function, over a map of...
                    lambda m:list(m), a)  #list made for mthe strings m
                   ) if i                 #truthy values only (otherwise the outer map will padd with None.
       ])

Answer 22

Oracle SQL, 195 bytes

    select listagg(b,'') within group(order by l,o) from(select substr(a,level,1) b,level l,o from i start with length(a)>0 connect by prior a=a and level<=length(a) and prior sys_guid() is not null)

Takes its input from a table named i with columns a (containing the string) and o (order of the string):

    create table i (a varchar2(4000), a integer)

Explanation:
We're exploiting CONNECT BY to break up the strings into each of the characters making them up. PRIOR SYS_GUID() being NOT NULL ensures we don't end up stuck in a loop.
We then concatenate the single characters with LISTAGG but we shuffle them around with an ORDER BY clause, ordering them first by their position in the original string and only then by the string they came from.

Not as short as the other answers but SQL isn't really meant as a string manipulation language :)

Answer 23

Perl 5, 28 bytes

26 bytes code + 2 for -0n.

s/^./!print$&/gem while/./

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Answer 24

R, 73 bytes

for(i in 1:max(nchar(s<-scan(,""))))for(j in seq(s))cat(substr(s[j],i,i))

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Explanation: very simple (but verbose), just loop through printing ith character of the jth string. Fortunately, substr returns an empty string if given an out-of-range input.

Answer 25

Python, 112 bytes

i=len(x)if len(x)>len(y) else len(y) h=0 a="" while h<i: if h<len(x) a+=x[h] if h<len(y): a += y[h] h+=1 print a

Answer 26

Perl 5, 53 bytes

$i=0,map{push@{$a[$i++]},$_}/./g for<>;print@$_ for@a

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Method

Creates a two dimensional array where the number of rows is equal to the length of the longest string and the maximum number of columns is equal to the number of strings. Then output each row of the array without spacing.

Answer 27

TXR Lisp, 20 bytes

(opip weave cat-str)

Run:

1> (opip weave cat-str)
#<intrinsic fun: 0 param + variadic>
2> [*1 "LYES" "APRONS"]
"LAYPERSONS"
3> [*1 "ABCDE" "a c" "" "123 567"]
"Aa1B 2Cc3D E567"
4> [*1 "\"\\n$?*" "" ",(.) "]
"\",\\(n.$)? *"

The weave function is lazy, so it returns a list, which is why we have to force the result to a string. Being lazy, it can weave infinite sequences. For instance, we can weave the even and odd natural numbers, which are themselves infinite lazy lists:

5> (take 20 (weave (range 2 : 2) (range 1 : 2)))
(2 1 4 3 6 5 8 7 10 9 12 11 14 13 16 15 18 17 20 19)

Answer 28

K (oK), 35 29 bytes

Solution:

{`c$r@&~^r:,/+(`i$x)[;!#,/x]}

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Example:

> {`c$r@&~^r:,/+(`i$x)[;!#,/x]}("ABCDE";"a c";"123 567")
"Aa1B 2Cc3D E567"
> {`c$r@&~^r:,/+(`i$x)[;!#,/x]}("\n$?*";"";",(.)\" ")
"\n,$(?.*)\" "
> {`c$r@&~^r:,/+(`i$x)[;!#,/x]}("POLLS";"EPEES")
"PEOPLELESS"

Explanation:

Use 2nd-level indexing to pull out indices from 0 to max (length of flattened list) across all input lists. Any indexing beyond the bound of the sub-list will return a null. Flip (rotates 90), flatten, and then pull out the non-null results.

Notes:

• I cast to integer (i$) so that we get useful nulls, as space () is considered null for a char list which means you cant tell nulls from valid spaces.
• Also I couldnt get the TIO to work with input (worked fine in the oK repl) so the TIO link includes the "ABCDE"... example.

Answer 29

Jq 1.5, 49 bytes

map(explode)|transpose|map(map(values)[])|implode

Explanation

                      # example input:          ["LYES","APRONS"]
  map(explode)        # make list of ordinals   [[76,89,69,83],[65,80,82,79,78,83]]
| transpose           # zip lists               [[76,65],[89,80],[69,82],[83,79],[null,78],[null,83]]
| map(map(values)[])  # rm nulls and flatten    [76,65,89,80,69,82,83,79,78,83]
| implode             # convert back to string  "LAYPERSONS"

Sample Run

$ paste input <(jq -Mrc 'map(explode)|transpose|map(map(values)[])|implode' input)
["SIMPLE"]                  SIMPLE
["POLLS","EPEES"]           PEOPLELESS
["LYES","APRONS"]           LAYPERSONS
["ABCDE", "a c", "123 567"] Aa1B 2Cc3D E567
["\"\\n$?*", "", ",(.)\" "] ",\(n.$)?"* 

$ echo -n 'map(explode)|transpose|map(map(values)[])|implode' | wc -c
  49    

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