RosettaCodeData/Task/Move-to-front-algorithm/Jq/move-to-front-algorithm-1.jq

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# Input is the string to be encoded, st is the initial symbol table (an array)
# Output: the encoded string (an array)
def m2f_encode(st):
reduce explode[] as $ch
( [ [], st]; # state: [ans, st]
(.[1]|index($ch)) as $ix
| .[1] as $st
| [ (.[0] + [ $ix ]), [$st[$ix]] + $st[0:$ix] + $st[$ix+1:] ] )
| .[0];
# Input should be the encoded string (an array)
# and st should be the initial symbol table (an array)
def m2f_decode(st):
reduce .[] as $ix
( [ [], st]; # state: [ans, st]
.[1] as $st
| [ (.[0] + [ $st[$ix] ]), [$st[$ix]] + $st[0:$ix] + $st[$ix+1:] ] )
| .[0]
| implode;