Shuffle string of digits

Question

Challenge

You have been given a string of digits 0-9.¹ Your task is to shuffle this string, but every index must have a different value than it did before the string was shuffled.

For example:

In : 287492
Out: 892247

If this is not possible, return false or something similar. (null, undefined, etc.)

In : 131
Out: false

There is no upper bound on the length of the string, but you can assume you have unlimited computation time.

Your function must pass the following tests:

shuffle('2')                   => false
shuffle('88')                  => false
shuffle('794588888')           => false
shuffle('344999')              => for example, '999434'
shuffle('172830560542976539')  => for example, '271038650425697395'

Shortest code wins, and good luck!

---

¹ More specifically, the string would match /^[0-9]+$/.

Answer 1

K (ngn/k), 37 32 bytes

{$[|/x=r:x[,/|2 0N#<x]@<<x;0;r]}

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{ } function with argument x

$[ ; ; ] if-then-else

<x "grade" - the sorting permutation for x

<<x "rankings" - the inverse of the sorting permutation

2 0N# split in two halves (or when length is odd - only approximately)

| swap the halves

,/ concatenate

x[ ] use as indices in x

..@<<x use <<x as indices in the previous result (a@b is alternative syntax for a[b])

r: assign to r - the potential result

x=r boolean list of which elements of x are equal to their counterparts in r

|/ or-reduction, i.e. "any?"

Answer 2

05AB1E, 7 bytes

Like the Pyth answer, outputs all possible shuffled strings or digits.

œʒø€Ëà_

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Explanation

œ       Permutations of the input
 ʒ      Filter such that:
  ø        Zipping with the original input
   €Ë      And comparing at corresponding indices
     à_    are all unequal.

Answer 3

Pyth, 9 bytes

f.AnVQT.p

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Outputs all possible strings that meet the criteria given in the question. This results in an empty list for the false cases.

Answer 4

Pyth, 7 bytes

-VI#Q.p

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Takes input as a list of digit-characters. For example:

['1', '2', '3']

Output: all possible derangements, with multiplicity for related characters.

• .p: Generate all permutations.

• #: Filter on

• I: Invariant under

• -V ... Q: Removing all characters that are at the same position in the input.

Answer 5

Jelly, 6 bytes

Œ!nẠ¥Ƈ

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Answer 6

JavaScript (Node.js), 125 bytes

e=>[...Array(i=2+e|0)].every(_=>(s=[...q=(--i+'').slice(1)]).some((_,j)=>_==e[j])|s.sort()+''!=[...e].sort()||console.log(q))

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Answer 7

Python 2, 83 80 bytes

lambda l:[p for p in permutations(l)if all(map(cmp,l,p))]
from itertools import*

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Goes through all permutation of the string, and keeps the ones that are different to the original string at every index.

Answer 8

PHP, 152 141 bytes

$a=count_chars($s=$argn,1);rsort($a);$a[0]*2<=strlen($s)?:die;for($s=$t=str_split($s);$s!=array_diff_assoc($s,$t);)shuffle($t);echo join($t);

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A bit lengthy but it's my first approach, will think more about it later

• displays empty string (exits) if impossible (if the most frequent number occurence is more than half of length of the string)
• uses an array approach and shuffles until it finds a proper result

EDIT: fixed an error in string length var attribution (missing brackets) + improved while condition for +1 byte

EDIT2: saved 1 byte, since brackets were mandatory for ternary condition, an if is now shorter

EDIT3: saved 11 bytes with the help of this answer by Titus to a closely related question

Answer 9

JavaScript (Node.js), 187 bytes

e=>{for(b=a=e.slice().sort(),a=+a.join(""),b=+b.reverse().join("");a<=b;){if(k=(a+"").split("").map(a=>+a),b==k.slice().sort((a,e)=>e-a).join("")&&e.every((a,e)=>a!=+k[e]))return a;a++}}

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-8 bytes thanks VFDan

JavaScript (Node.js), 179 bytes

e=>{for(b=a=e.slice().sort(),a=+a.join``,b=+b.reverse().join``;a<=b;){if(k=(a+"").split``.map(a=>+a),b==k.slice().sort((a,e)=>e-a).join``&&e.every((a,e)=>a!=+k[e]))return a;a++}}

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