Perfect shuffle: Difference between revisions
→{{header|jq}}
Line 1,370:
1024 10
10000 300</pre>
=={{header|jq}}==
{{works with|jq}}
A small point of interest in the following is the `recurrence` function as it is generic.
<lang jq>def perfect_shuffle:
. as $a
| if (length % 2) == 1 then "cannot perform perfect shuffle on odd-length array" | error
else (length / 2) as $mid
| reduce range(0; $mid) as $i (null;
.[2*$i] = $a[$i]
| .[2*$i + 1] = $a[$mid+$i] )
end;
# How many iterations of f are required to get back to . ?
def recurrence(f):
def r:
# input: [$init, $current, $count]
(.[1]|f) as $next
| if .[0] == $next then .[-1] + 1
else [.[0], $next, .[-1]+1] | r
end;
[., ., 0] | r;
def count_perfect_shuffles:
[range(0;.)] | recurrence(perfect_shuffle);
(8, 24, 52, 100, 1020, 1024, 10000, 100000)
| [., count_perfect_shuffles]</lang>
{{out}}
<pre>
[8,3]
[24,11]
[52,8]
[100,30]
[1020,1018]
[1024,10]
[10000,300]
[100000,540]
</pre>
=={{header|Julia}}==
| |||