Create a shifter

Question

To "shift" over a number n places, do the following:

Remove the last n digits
Add n copies of the first digit to the beginning of the number

For example, to shift the number 31415 three places, take out the last three digits to get 31, and then add three more copies of the first digit, 3, to the end, giving 33331.

If the number is negative, digits should be taken from the left instead, and the first digit should be "filled in" from the right. For example, the string 31415 shifted over -3 places gives 15555.

If the number is 0, no change should be made.

If the shift is more than the length of the program, then digits that were filled in might start to be removed. This means that if the number given is more than the length of the string, no further changes will be made after the entire string becomes a single digit.

The challenge

Given two numbers, n and s, return n shifted over s places.

Test cases

   n,  s -> result
7243,  1 -> 7724
 452, -1 -> 522
  12,  1 -> 11
 153,  4 -> 111

This is code-golf, so the shortest valid submission (measured in bytes) wins.

I don't think I understand what the "shifting" does. This is tagged [binary], which makes me think it has something to do with binary shifts. Maybe it would help to also display the numbers in binary in the test cases? — Esolanging Fruit, Jul 18, 2017 at 22:19
It's shifting and "stretching" the first or last digit. What's unclear? — Luis Mendo, Jul 18, 2017 at 22:29
Shifting is well defined: integer multiplication or division by a power of the base. But none of the test cases work, so this question appears to use an idiosyncratic definition and not say what it is. — Peter Taylor, Jul 19, 2017 at 6:54

Adám · Accepted Answer · 2017-07-18 22:28:28Z

APL (Dyalog), 32 bytes

Anonymous function which takes the sift as left argument and the number (as a string) as right argument.

{a←|⍺⋄(≢⍵)↑(a-⍺)↓(a⍴⊃⍵),⍵,a⍴⊃⌽⍵}

Try it online!

{ anonymous function where ⍺ and ⍵ are left and right arguments

|⍺ the absolute value of the shift

a← store in a

⋄ then

⌽⍵ reverse the number

⊃ pick the first (i.e. last) digit

a⍴ reshape it to length a

⍵, prepend the number

(…), prepend the following:

⊃⍵ the first digit

a⍴ reshape it to length a

(…)↓ drop the following number of characters:

a-⍺ a minus the shift

(…)↑ take the following number of characters:

≢⍵ the length of the original number

Chas Brown · Accepted Answer · 2017-07-19 01:38:56Z

2

Python 2, 50 bytes

lambda n,s:(n[0]*s+n+n[-1]*-s)[-s*(s<0):][:len(n)]

Try it online!

edited Jul 19, 2017 at 1:38

answered Jul 19, 2017 at 1:24

Chas Brown

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nimi · Accepted Answer · 2017-07-19 18:48:38Z

Haskell, 69 bytes

s#n|l<-[1..abs n]=take(length s)$drop(-2*n)$(s!!0<$l)++s++(last s<$l)

Takes the number as a string. Try it online!

How it works:

s#n                         -- s: input number as a string
                            -- n: shift amount

(s!!0<$l)++s++(last s<$l)   -- make a string:
                            -- n times the first digit, the whole number, n times the last digit
                            -- e.g. "567" 2 -> 5556777
drop(-2*n)                  -- drop the first (-2 * n) chars, i.e. 0 if n>0
take(length s)              -- take as may chars as there are in s

Luis Mendo · Accepted Answer · 2017-07-19 22:44:08Z

2

MATL, 12 bytes

tn:i-yn1&Xl)

Inputs are: number to be shifted as a string; amount of shifting as a number.

Try it online! Or verify all test cases.

Consisder inputs '452 and '-1'.

t     % Implicitly input string. Duplicate
      % STACK: '452', '452'
n     % Number of elements
      % STACK: '452', 3
:     % Range
      % STACK: '452', [1 2 3]
i     % Input number
      % STACK: '452', [1 2 3], -1
-     % Subtract, element-wise
      % STACK: '452', [2 3 4]
y     % Duplicate from below
      % STACK: '452', [2 3 4], '452'
n     % Number of elements
      % STACK: '452', [2 3 4], 3
1     % Push 1
      % STACK: '452', [2 3 4], 3, 1
&Xl   % Clamp, with three inputs. Applies min function, then max
      % STACK: '452', [2 3 3]
)     % Reference indexing. Implicitly display
      % STACK: '522'

edited Jul 19, 2017 at 22:44

answered Jul 19, 2017 at 8:36

Luis Mendo

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1

\$\begingroup\$ This is by far the least amount of bytes good job! \$\endgroup\$
– K Split X
Jul 19, 2017 at 19:44
\$\begingroup\$ @KSplitX Thanks! BTW I just added an explanation \$\endgroup\$
– Luis Mendo
Jul 19, 2017 at 21:17

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Community · Accepted Answer · 2020-06-17 09:04:33Z

1

J, 37 bytes

This was one of those situations in J where an explicit verb seemed like the right (the only?) choice, but I would love to know if there's a tacit rewrite of this:

4 :'(-x)(|.!.((x>0)&{({:,{.)":y))":y'

J's built in shift verb allows you to configure the "fill" character:

|.!.f  NB. f is the fill character

The logic to determine whether to use the first or last char as the fill character is straightforward

(x>0)&{ ({: , {.)

Try it online!

edited Jun 17, 2020 at 9:04

CommunityBot

1

answered Jul 19, 2017 at 6:37

Jonah

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miles · Accepted Answer · 2017-07-19 11:37:27Z

1

J, 23 bytes

(_&(]{.,],{:)~|)}.~_2*]

Input n and the output are strings containing the numbers.

Try it online!

Explanation

(_&(]{.,],{:)~|)}.~_2*]  Input: 'integer n' as a string (LHS), integer s (RHS)
(              )         Extend 'n' by copying its head and tail 's' times
              |            Abs(s)
 _&(]       )~             Nest 'Abs(s)' times on 'n'
          {:                 Tail
        ],                   Append the tail to itself
     {.                      Head
       ,                     Prepend the head to the previous
                   _2*]  Multiply 's' by -2
                }.~      Drop abs(-2*s) from the head if 's' < 0 else from the tail

answered Jul 19, 2017 at 11:37

miles

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\$\begingroup\$ beautiful. i suspected there was a better approach than mine... \$\endgroup\$
– Jonah
Jul 19, 2017 at 13:58
\$\begingroup\$ although i notice you take n as a string which (possibly incorrectly ) id assumed was not allowed. though it would have saved me only 4 chars... \$\endgroup\$
– Jonah
Jul 19, 2017 at 14:12

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ovs · Accepted Answer · 2017-07-19 18:15:16Z

1

Retina, 61 bytes

\d+¶
$*1¶
+`(?<!-).¶(.)(.*).
¶$1$1$2
-

+`.¶.(.*)(.)$
¶$1$2$2

Try it online!

answered Jul 19, 2017 at 18:15

ovs

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Emigna · Accepted Answer · 2017-07-21 09:13:16Z

05AB1E, 16 bytes

0‹©iR}¹ÄF¨¬ì}®iR

Try it online!

Explanation

0‹                 # input_1 is negative
  ©                # store a copy in register
   iR}             # if true (input_1 is negative), reverse input_2
      ¹ÄF          # abs(input_1) times do
         ¨         # remove the last element
          ¬ì       # prepend the head
            }      # end loop
             ®iR   # if input_1 was negative, reverse result

musicman523 · Accepted Answer · 2017-07-19 01:01:46Z

0

Python 2, 87 bytes

f=lambda n,s:s<0and f(n[::-1],-s)[::-1]or n[0]*min(len(n),s)+n[:[0,len(n)-s][len(n)>s]]

Try it online!

Takes the number as a string, and the shift as an integer. Returns a string.

I tried embedding the reversal inside the function rather than making a recursive call, but I couldn't seem to get it right.

answered Jul 19, 2017 at 1:01

musicman523

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wrymug · Accepted Answer · 2017-07-19 01:15:13Z

0

Python 3, 73 bytes

f=lambda s,i:(f(s+1,i[1:]+i[-1])if s<0else f(s-1,i[0]+i[:-1]))if s else i

Try it online!

answered Jul 19, 2017 at 1:15

wrymug

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ბიმო · Accepted Answer · 2017-07-19 02:02:41Z

0

Haskell, 108 bytes

Oh well, this went worse than I thought..

n#s=print$show n&s
r=reverse
n&s|s<0=r$r n&abs s|(a:b,c)<-splitAt s n=take(length n)$(a<$[0..s])++b++c|1>0=n

Try it online!

Ungolfed

n # s = print $ show n & s
n & s
  | s < 0                = reverse (reverse n & abs s)
  | (a:b,c)<-splitAt s n = take (length n) (replicate s a ++ b ++ c)
  | otherwise            = n

edited Jul 19, 2017 at 2:02

answered Jul 19, 2017 at 1:55

ბიმო

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NikoNyrh · Accepted Answer · 2017-07-19 08:20:04Z

0

Clojure, 121 bytes

#(let[T(if(pos? %2)reverse vec)](apply str(concat(repeat %2(first %))(T(drop(Math/abs %2)(T %)))(repeat(- %2)(last %)))))

Ouch, nasty to deal with negative inputs as well.

answered Jul 19, 2017 at 8:20

NikoNyrh

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Community · Accepted Answer · 2020-06-17 09:04:33Z

Pyth, 28 bytes

AQ=Y<+*hJ?K<0H`G_`GHJlJ?KY_Y

Try it online or test some inputs

Explanation

AQ=Y<+*hJ?K<0H`G_`GHJlJ?KY_Y
AQ                           | Split Q into 2 parts, G and H.
        J?K<0H`G_`G          | If 0 < H, J = str(G). Else, J = reverse(str(G)). Return J
       h                     | Find 1st element
      *            H         | Repeat H times
     +              J        | Concatenate with J
    <                lJ      | Find 1st length(J) elements
  =Y                         | Assign to Y.
                       ?KY_Y | If K, implicit print Y. Else implicit print reverse(Y).

Magic Octopus Urn · Accepted Answer · 2017-07-19 18:31:48Z

0

05AB1E, 33 bytes

ÄF¹0‹©i¨ë¦}}²®i¤ë¬}sg¹Ä‚Ws\×®i«ëì

Try it online!

05AB1E is not so hot with conditionals.

answered Jul 19, 2017 at 18:31

Magic Octopus Urn

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Justin Mariner · Accepted Answer · 2017-07-21 05:49:05Z

JavaScript, 80 bytes

(n,s,k=n.length,p=s<=0)=>n.slice(p*-s,p?k:-s)[p?"padEnd":"padStart"](k--,n[p*k])

Takes input as a string representation of the number and a numerical "shift" amount. Returns a string.

Test Snippet

let f=
(n,s,k=n.length,p=s<=0)=>n.slice(p*-s,p?k:-s)[p?"padEnd":"padStart"](k--,n[p*k])

I.value="31415";J.value="3";D.oninput()

<div id=D oninput="O.value=I.value.length&J.value.length?f(I.value,+J.value):''">n: <input id=I size=10> s: <input id=J size=2><br><input id=O disabled>

Stack Exchange Network

Create a shifter

The challenge

Test cases

15 Answers 15

APL (Dyalog), 32 bytes

Python 2, 50 bytes

Haskell, 69 bytes

MATL, 12 bytes

J, 37 bytes

J, 23 bytes

Explanation

Retina, 61 bytes

05AB1E, 16 bytes

Python 2, 87 bytes

Python 3, 73 bytes

Haskell, 108 bytes

Ungolfed

Clojure, 121 bytes

Pyth, 28 bytes

05AB1E, 33 bytes

JavaScript, 80 bytes

Test Snippet

Your Answer

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code-golf
math
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Hot Network Questions

Create a shifter

The challenge

Test cases

15 Answers 15

APL (Dyalog), 32 bytes

Python 2, 50 bytes

Haskell, 69 bytes

MATL, 12 bytes

J, 37 bytes

J, 23 bytes

Explanation

Retina, 61 bytes

05AB1E, 16 bytes

Python 2, 87 bytes

Python 3, 73 bytes

Haskell, 108 bytes

Ungolfed

Clojure, 121 bytes

Pyth, 28 bytes

05AB1E, 33 bytes

JavaScript, 80 bytes

Test Snippet

Your Answer

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