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Reading a book is easy, but printing a book can be a bit tricky. When printing a booklet, the printer needs to have the pages arranged in a certain manner in order to be read from left to right. The way this is done is using a pattern like below

n, 1, 2, n-1, n-2, 3, 4, n-3, n-4, 5, 6, n-5, n-6, 7, 8, n-7, n-8, 9, 10, n-9, n-10, 11, 12, n-11…

Test Cases

4 page booklet: 4, 1, 2, 3

8 page booklet: 8,1,2,7,6,3,4,5

12 page booklet: 12,1,2,11,10,3,4,9,8,5,6,7

16 page booklet: 16,1,2,15,14,3,4,13,12,5,6,11,10,7,8,9

20 page booklet: 20,1,2,19,18,3,4,17,16,5,6,15,14,7,8,13,12,9,10,11

Task

Your task is to, given an integer n that is a multiple of 4, display an array of numbers that could be used to print a book of n pages.

Note: As long as the output generates the correct numbers, whether delimited by spaces, commas, hyphens, or parenthesis, any method to getting to a solution can be used

This is a question so answers will be scored in bytes, with the fewest bytes winning.

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  • \$\begingroup\$ Are we guaranteed that input will always be divisible by 4 or even an even number? Either way, could you add a few more test cases, please? And welcome to PPCG :) \$\endgroup\$ – Shaggy Aug 6 '17 at 23:51
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    \$\begingroup\$ Welcome to PPCG and nice first challenge! Note that we recommend proposing new challenges in the sandbox before posting them. \$\endgroup\$ – Oliver Ni Aug 6 '17 at 23:57
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    \$\begingroup\$ Your input needs to be a multiple of 4 \$\endgroup\$ – tisaconundrum Aug 6 '17 at 23:57
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    \$\begingroup\$ Would be nice (but maybe trivial) to support any value, filling with blank pages if needed (another challenge, maybe?) \$\endgroup\$ – Barranka Aug 7 '17 at 14:56
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    \$\begingroup\$ Can we delimit the array with a space, hyphen, or other delimiter instead of a comma? \$\endgroup\$ – TehPers Aug 7 '17 at 20:01

31 Answers 31

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Python 2, 50 bytes

A port of Arnauld's JS answer.

f=lambda n,k=1:n>k and[n,k,k+1,n-1]+f(n-2,k+2)or[]

Try it online!

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    \$\begingroup\$ n-k-1 is n+~k. \$\endgroup\$ – Mr. Xcoder Aug 7 '17 at 8:20

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