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Ingy döt Net 2023-07-01 11:58:00 -04:00
parent 7387c8f97b
commit cb5bb5e222
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Task/Van-Eck-sequence/ALGOL-68/van-eck-sequence.alg Normal file
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BEGIN # find elements of the Van Eck Sequence - first term is 0, following #
# terms are 0 if the previous was the first appearance of the element #
# or how far back in the sequence the last element appeared #
# returns the first n elements of the Van Eck sequence #
OP VANECK = ( INT n )[]INT:
BEGIN
[ 1 : IF n < 0 THEN 0 ELSE n FI ]INT result; FOR i TO n DO result[ i ] := 0 OD;
[ 0 : UPB result ]INT pos; FOR i FROM 0 TO n DO pos[ i ] := 0 OD;
FOR i FROM 2 TO n DO
INT j = i - 1;
INT prev = result[ j ];
IF pos[ prev ] /= 0 THEN
# not a new element #
result[ i ] := j - pos[ prev ]
FI;
pos[ prev ] := j
OD;
result
END # VANECK # ;
# construct the first 1000 terms of the sequence #
[]INT seq = VANECK 1000;
# show the first and last 10 elements #
FOR i TO 10 DO print( ( " ", whole( seq[ i ], 0 ) ) ) OD;
print( ( newline ) );
FOR i FROM UPB seq - 9 TO UPB seq DO print( ( " ", whole( seq[ i ], 0 ) ) ) OD;
print( ( newline ) )
END