Discussion on: Daily Challenge #53 - Faro Shuffle

[La blatte]

A bit of golf:

f=a=>a.map((_,i)=>a[i/2+i%2*(a.length/2-.5)])

It works like this:

• .map((_,i) : "i" will be the index of the current element, we don't need to work with the value here
• We return a value located inside the input, at the following index:
  • If we are in an odd space, the targeted index will be i/2 + true * (a.length / 2 + 0.5). Thanks to coercion, "true" will be translated to 1, hence we will fetch the (a.length / 2 + 0.5)+i/2th index
  • Else if we are in an even space, the target will be i/2 + false * (a.length / 2 + 0.5), translated to i/2 + 0 * (a.length / 2 + 0.5) (hence, i/2)

The return will then be the following:

f(['ace', 'two', 'three', 'four', 'five', 'six'])
// ["ace", "four", "two", "five", "three", "six"]

f([...'1234567890abcdef'])
["1", "9", "2", "0", "3", "a", "4", "b", "5", "c", "6", "d", "7", "e", "8", "f"]

[Alvaro Montoro]

Taking into account that the input is an array, you could save some bytes by replacing [...a] with just a (for golf purposes).

Apart from that, the solution seems really specific to the problem, and doesn't work for different arrays. For example:

f(['ace', 'two', 'three', 'four', 'five', 'six', 'seven', 'eight'])
//["ace", "four", "two", "five", "three", "six", "four", "seven"]
// there are 2 "four" and no "eight"

[La blatte]

Thanks a lot for the input! The problem was in the 2.5 usage, which had to be replaced with a.length/2-.5. I updated my answer!

[Andrea Griffini]

You can shorten the index computation to:

i+i%2*a.length>>1