Bouncing in an array

Question

Introduction

Arrays can also be seen as a field for a bouncing ball. This of course sounds very vague, so here is an example of an input:

[1, 2, 3, 4, 5, 6, 7, 8, 9]
[9, 8, 7, 6, 5, 4, 3, 2, 1]
[1, 2, 3, 4, 5, 6, 7, 8, 9]

The challenge is to output the bounced arrays. These are made from diagonal patterns which bounce at the edges of the field. This path is pointed upwards. The path for the first bounced array (in which the path is directly bounced off the egde), is:

[1, -, -, -, 5, -, -, -, 9]
[-, 8, -, 6, -, 4, -, 2, -]
[-, -, 3, -, -, -, 7, -, -]

From left to right, this would result in [1, 8, 3, 6, 5, 4, 7, 2, 9]. This is our first bounced array. The path for the second bounced array:

[-, 2, -, -, -, 6, -, -, -]
[9, -, 7, -, 5, -, 3, -, 1]
[-, -, -, 4, -, -, -, 8, -]

This results in [9, 2, 7, 4, 5, 6, 3, 8, 1]. The path for the third bounced array is:

[-, -, 3, -, -, -, 7, -, -]
[-, 8, -, 6, -, 4, -, 2, -]
[1, -, -, -, 5, -, -, -, 9]

This results in [1, 8, 3, 6, 5, 4, 7, 2, 9]. So the three bounced arrays are:

[1, 8, 3, 6, 5, 4, 7, 2, 9]
[9, 2, 7, 4, 5, 6, 3, 8, 1]
[1, 8, 3, 6, 5, 4, 7, 2, 9]

Task

Given at least 1 array containing only non-negative integers, with all the arrays having the same length, output all the bounced arrays.

Test cases

Test case 1:

Input:                       Output:
[1, 2, 3, 4, 5]              [1, 7, 3, 9, 5]
[6, 7, 8, 9, 0]              [6, 2, 8, 4, 0]


Input:                       Output:
[1, 2, 3, 4, 5]              [1, 2, 3, 4, 5]


Input:                       Output:
[0, 0, 0, 0, 0, 0, 0, 0]     [0, 9, 0, 9, 0, 9, 0, 100]
[9, 9, 9, 9, 9, 9, 9, 100]   [9, 0, 9, 0, 9, 0, 9, 0]
[0, 0, 0, 0, 0, 0, 0, 0]     [0, 9, 0, 9, 0, 9, 0, 100]


Input:                       Output:
[0, 1, 2, 3, 4, 5]           [0, 7, 14, 9, 4, 11]
[6, 7, 8, 9, 10, 11]         [6, 1, 8, 15, 10, 5]
[12, 13, 14, 15, 16, 17]     [12, 7, 2, 9, 16, 11]


Input:                       Output:
[0, 0, 0, 0, 0, 0]           [0, 2, 2, 6, 2, 6]
[1, 2, 3, 4, 5, 6]           [1, 0, 3, 2, 5, 2]
[2, 2, 2, 2, 2, 2]           [2, 2, 0, 4, 2, 4]
[9, 8, 7, 6, 5, 4]           [9, 2, 3, 0, 5, 2]

This is code-golf, so the submission with the least amount of bytes wins!

Can you please add a three-array testcase where the last array is different then the first, and a four-array testcase? — ETHproductions, Jan 22, 2016 at 19:11
I can't find the problem description. Can anyone tell me where it is? — feersum, Jan 22, 2016 at 19:14
@LuisMendo it's the only way to bounce, at line 0 it can't go up more — edc65, Jan 22, 2016 at 22:15

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

7

Pyth, 17 bytes

>lQC.e.>bkC+_PtQQ

Explanation:

                      implicit: Q=input
>                     First
  l Q                   len(Q) elements of the
  C .e                  Transpose of enumerated map lambda b,k:
       .>                 Rotate the kth element rightwards by
          b
          k               k.
       C +              Transpose of: Q concatenated to
           _ P t Q        itself reversed without first and last elements.
           Q

Try it here.

edited Jun 17, 2020 at 9:04

CommunityBot

1

answered Jan 22, 2016 at 18:55

lirtosiast

21.5k5 gold badges50 silver badges127 bronze badges

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edc65 · Accepted Answer · 2016-01-22 23:00:01Z

JavaScript (ES6), 70

a=>a.map((r,k)=>r.map((e,j)=>(a[k-=d]||a[d=-d,k-=d+d]||r)[j],d=1,++k))

TEST

F = a=>a.map((r,k)=>r.map((e,j)=>(a[k-=d]||a[d=-d,k-=d+d]||r)[j],d=1,++k))

test = [{
  I: [
    [1, 2, 3, 4, 5],
    [6, 7, 8, 9, 0]
  ],
  O: [
    [1, 7, 3, 9, 5],
    [6, 2, 8, 4, 0]
  ]
}, {
  I: [
    [1, 2, 3, 4, 5]
  ],
  O: [
    [1, 2, 3, 4, 5]
  ]
}, {
  I: [
    [0, 0, 0, 0, 0, 0, 0, 0],
    [9, 9, 9, 9, 9, 9, 9, 100],
    [0, 0, 0, 0, 0, 0, 0, 0]
  ],
  O: [
    [0, 9, 0, 9, 0, 9, 0, 100],
    [9, 0, 9, 0, 9, 0, 9, 0],
    [0, 9, 0, 9, 0, 9, 0, 100]
  ]
}, {
  I: [
    [0, 1, 2, 3, 4, 5],
    [6, 7, 8, 9, 10, 11],
    [12, 13, 14, 15, 16, 17]
  ],
  O: [
    [0, 7, 14, 9, 4, 11],
    [6, 1, 8, 15, 10, 5],
    [12, 7, 2, 9, 16, 11]
  ]
}, {
  I: [
    [0, 0, 0, 0, 0, 0],
    [1, 2, 3, 4, 5, 6],
    [2, 2, 2, 2, 2, 2],
    [9, 8, 7, 6, 5, 4]
  ],
  O: [
    [0, 2, 2, 6, 2, 6],
    [1, 0, 3, 2, 5, 2],
    [2, 2, 0, 4, 2, 4],
    [9, 2, 3, 0, 5, 2]
  ]
}];

console.log = x => O.textContent += x + '\n';

test.forEach(t => {
  var r = F(t.I),
    ok = r.join `\n` == t.O.join `\n`
  console.log((ok ? 'OK' : 'KO') + '\nInput\n' + t.I.join `\n` + '\nOutput\n' + r.join `\n` + '\n')
})

<pre id=O></pre>

Martin Ender · Accepted Answer · 2016-01-22 20:46:28Z

3

CJam, 31 30 bytes

q~__W%1>W<+_z,_@*<zee::m>z\,<p

Input and output as a list of CJam-style arrays.

Test it here.

Most definitely golfable...

edited Jan 22, 2016 at 20:46

answered Jan 22, 2016 at 19:32

Martin Ender

197k65 gold badges444 silver badges970 bronze badges

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Dennis · Accepted Answer · 2016-01-24 06:39:30Z

3

Jelly, 29 25 24 bytes

ṖḊm-³;Z
,ZL€R_€/‘ż€Çị/€€

Thanks for @Sp3000 for helping me golf off 5 bytes!

Try it online!

edited Jan 24, 2016 at 6:39

answered Jan 22, 2016 at 21:14

Dennis

210k41 gold badges370 silver badges823 bronze badges

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Connor Clark · Accepted Answer · 2016-01-23 03:25:23Z

2

Ruby (2.2.2p95), 124 bytes

->*a{b=a.length;b<2?a:b.times.map{|i|d=i>0?-1:1;c=i;a[0].length.times.map{|j|r=a[c][j];c+=d;d*=-1if c==0||c==a.length-1;r}}}

This could probably be a lot better. I'll figure out how later!

answered Jan 23, 2016 at 3:25

Connor Clark

1513 bronze badges

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ETHproductions · Accepted Answer · 2016-01-23 21:00:09Z

Japt, 55 49 41 39 bytes

Wow, that was both really tricky and insanely fun.

C=2*Nl -2Nw £YoY+Ul)£NgLmX%CC-X%C)gY} ·

Test it online!

Outputs in reverse order to the examples. This will break slightly on inputs of more than 100 arrays; hopefully this doesn't make too much difference.

           // Implicit: N = array of input arrays, U = first input array, J = -1, L = 100
           // Let's use the first example. 3 input arrays, each of length 9.
C=2*Nl -2  // Set variable C to 2*N.length - 2. In the example, C is 4.
Nw      }  // Reverse N and map each index Y to:
YoY+Ul)    //  Create the range [Y...U.length+Y).
           //  The first time through (Y=0), we have   [0, 1, 2, 3, 4, 5, 6, 7, 8]
£       }  //  Map each item X and index Y to:
X%C        //   Take X mod C.                          [0, 1, 2, 3, 0, 1, 2, 3, 0]
C-X%C      //   Take C - (X mod C).                    [4, 3, 2, 1, 4, 3, 2, 1, 4]
Lm         //   Take the minimum of these and 100.     [0, 1, 2, 1, 0, 1, 2, 1, 0]
Ng         //   Get the array at the resulting index.
gY         //   Get the item at index Y in this array. [1, 8, 3, 6, 5, 4, 2, 7, 9]
·          // Join the result with newlines. I guess this isn't necessary, but it helps with readability.

Non-competing version, 36 bytes

C=J+Nl)òC±C ®óUl)£NgLmX%CC-X%C)gY} ·

I had implemented these two number functions prior to the challenge:

ò - same as o, but returns [X..Y] instead of [X..Y)
ó - same as o, but returns [X..X+Y) instead of [X..Y)

But due to a misplaced 0, they were buggy and always returned empty arrays. This has now been fixed.

Test it online!

Orez · Accepted Answer · 2017-02-16 16:09:47Z

2

Python 2, 107 106 108 105 104 bytes

(Dropped some extra parens) (Wrong starting location (ب_ب) ) (already had a list of that length)

def b(a):
 r,e=len(a)-1,enumerate
 print[[a[abs((i-o-r)%(r*2or 1)-r)][i]for i,_ in e(q)]for o,q in e(a)]

It's legal to have the input as an argument to a function, right? This is my first time submitting my code golf answer.

edited Feb 16, 2017 at 16:09

answered Jan 23, 2016 at 20:32

Orez

4812 silver badges8 bronze badges

\$\begingroup\$ Yes it is legal :) \$\endgroup\$
– Adnan
Jan 24, 2016 at 2:16

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lstefano · Accepted Answer · 2016-06-30 12:10:54Z

1

APL, 33 chars

{(⍳≢⍵){0⌷(⍺-⍳≢⍉⍵)⊖⍵⍪1↓¯1↓⊖⍵}¨⊂↑⍵}

Assume ⎕IO←0. The idea is that the bouncing movement can be obtained by simple shift upward of a matrix, if the original matrix is augmented along the first dimension with the matrix reversed with its first and last row shaved. Graphically:

1 - - - - - 1 - - - -
- 2 - - - 2 - 2 - - -
- - 3 - 3 - - - 3 - 3
- - - 4 - - - - - 4 -

from

1 - - - - - 1 - - - -
- 2 - - - - - 2 - - -
- - 3 - - - - - 3 - -
- - - 4 - - - - - 4 -
- - - - 3 - - - - - 3
- - - - - 2 - - - - -

In APL reverse and upward rotate are the same symbol: ⊖.

answered Jun 30, 2016 at 12:10

lstefano

9105 silver badges6 bronze badges

\$\begingroup\$ USE THE FIRST STEFANO. ⊃ instead of 0⌷. \$\endgroup\$
– Adalynn
Jul 31, 2017 at 22:34
\$\begingroup\$ I am afraid "first" and "0⌷" give two very different results when applied to a nested array. Try it for yourself. First vs. 0⌷ \$\endgroup\$
– lstefano
Aug 2, 2017 at 9:30

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NikoNyrh · Accepted Answer · 2016-12-27 19:55:32Z

1

Clojure, 125 bytes

Wow, this accumulated characters quite fast.

(fn[v](let[H(count v)r range R(r H)](for[i R](map #((v %2)%)(r(count(v 0)))(drop i(cycle(concat R(reverse(r 1(dec H))))))))))

Just trying to save bytes by let-defining frequently used values.

answered Dec 27, 2016 at 19:55

NikoNyrh

2,6419 silver badges8 bronze badges

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Erik the Outgolfer · Accepted Answer · 2018-09-23 20:26:07Z

0

Jelly*, 15 bytes

JṚŒḄṖṙ’Ʋị⁸Jị"$€

Try it online!

^{* Newer version}

answered Sep 23, 2018 at 20:26

Erik the Outgolfer

40.6k5 gold badges42 silver badges122 bronze badges

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Stack Exchange Network

Bouncing in an array

Introduction

Task

Test cases

10 Answers 10

Pyth, 17 bytes

JavaScript (ES6), 70

CJam, 31 30 bytes

Jelly, 29 25 24 bytes

Ruby (2.2.2p95), 124 bytes

Japt, 55 49 41 39 bytes

Non-competing version, 36 bytes

Python 2, 107 106 108 105 104 bytes

APL, 33 chars

Clojure, 125 bytes

Jelly*, 15 bytes

Your Answer

Not the answer you're looking for? Browse other questions tagged
code-golf
array
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Hot Network Questions

Bouncing in an array

Introduction

Task

Test cases

10 Answers 10

Pyth, 17 bytes

JavaScript (ES6), 70

CJam, 31 30 bytes

Jelly, 29 25 24 bytes

Ruby (2.2.2p95), 124 bytes

Japt, 55 49 41 39 bytes

Non-competing version, 36 bytes

Python 2, 107 106 108 105 104 bytes

APL, 33 chars

Clojure, 125 bytes

Jelly*, 15 bytes

Your Answer

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