13
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Add the four basic operators $\times\div+\,\;-$ and optionally brackets to:

$10 \quad 9 \quad 8 \quad 7 \quad 6 \quad 5 \quad 4 \quad 3 \quad 2 \quad 1$

To get the total $2017$.

Rules:

  • Look for the simplest solution - i.e. the least amount of characters (ignoring spaces). Please include your character count in your answer.
  • Keep the order; do not add or combine numbers.
  • Use all four operators at least once.

Credit for initial concept: Alex Bellos


Previous year: here.

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6
  • $\begingroup$ Is implicit multiplication allowed? $\endgroup$ Jan 1, 2017 at 12:11
  • $\begingroup$ For best solution you can mix up the numbers like 109X87+6543-21 $\endgroup$ Jan 1, 2017 at 13:27
  • 8
    $\begingroup$ As of 2017 Code Golf is invading puzzling. $\endgroup$
    – Zxyrra
    Jan 1, 2017 at 16:05
  • 1
    $\begingroup$ Just being curious about it: is there a known algorithm to solve it? (given inputs: list of possible numbers, desired result). I'm thinking about dynamic programing. Also don't know how I could call this problem to look for litterature. $\endgroup$
    – pltrdy
    Jan 2, 2017 at 11:57
  • $\begingroup$ @pltrdy Have you read this post? $\endgroup$
    – xzczd
    Jan 5, 2017 at 14:58

5 Answers 5

22
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This one is 20 characters:

$10×9×8×7 \div 6 \div 5×4×3 + 2 - 1$

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7
  • 6
    $\begingroup$ @Paparazzi thanks - I think I left my counting skills in 2016. $\endgroup$
    – Glorfindel
    Jan 1, 2017 at 12:42
  • 8
    $\begingroup$ Will work for the next two years as well (changing the final - to a x or +) $\endgroup$ Jan 1, 2017 at 15:26
  • $\begingroup$ @TomCarpenter And it would also work for 2013-2015 by flipping the sign for 2 and manipulating the operator for 1 accordingly. This should also be the shortest answer, considering it has no brackets. $\endgroup$
    – Reti43
    Jan 1, 2017 at 23:54
  • $\begingroup$ I wrote a script to try all combinations without parenthesis, this is the only one it finds. $\endgroup$
    – C5H8NNaO4
    Jan 2, 2017 at 2:35
  • $\begingroup$ @TomCarpenter no it would not: a - sign would be missing. $\endgroup$
    – Cœur
    Jan 2, 2017 at 11:36
15
$\begingroup$

One can even find $2017$ by using only 5 numbers given in the question without changing the order as below:

$9×8×7×4+1=2017$

Here are the actual answers for the question:

  1. $(10+9×8×7-6-5)×4+3+2×1=2017$ - 22 Chars

  2. $(10×9×8×7)\div((6×5)\div(4×3))+2-1=2017$ - 28 Chars

  3. $10×9×8×7×6\div5\div(4-3+2)+1=2017$ - 22 Chars

  4. $(10+9×8×7-6-5)×4+3+2\div1=2017$ - 22 Chars

  5. $10×9×8×7\div(6+5+4)×3×2+1=2017$ - 22 Chars

  6. $10-9+8×7×6×(5-4)×3×2\div1=2017$ - 22 Chars

  7. $(10-9+8)×7×(6-5+(4-3)×2)+1=2017$ - 26 Chars

  8. $(10+9)×8×(7+6)+5+4×3×(2+1)=2017$ - 26 Chars

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4
  • 2
    $\begingroup$ You can simplify some of those, considering a ÷ (b ÷ c) = a ÷ b × c and a ÷ (b × c) = a ÷ b ÷ c $\endgroup$ Jan 1, 2017 at 20:35
  • 2
    $\begingroup$ #3 has mismatching brackets $\endgroup$
    – vrwim
    Jan 2, 2017 at 0:49
  • $\begingroup$ Can you include the number of characters for each? $\endgroup$
    – IAmInPLS
    Jan 2, 2017 at 11:17
  • $\begingroup$ @IAmInPLS fixed all errors... $\endgroup$
    – Oray
    Jan 2, 2017 at 11:45
2
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22 characters:

$10×9×8×7×6÷5÷(4−3+2)+1$

There may be less, but pretty happy about this

There is also:

$10×9×8×7×6÷(5+4×3−2)+1$

Which is same length but slightly different

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1
$\begingroup$

(((10*9*8*7)/(6*5))*4*3)+2-1=2017

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1
$\begingroup$

2017 = 10+9+8+7+6+5+4+3+2+1+987+654+321

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1
  • $\begingroup$ While this is a rather interesting result, this is not an answer to the question. $\endgroup$ Jan 6, 2017 at 6:00

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