RosettaCodeData/Task/Hamming-numbers/UNIX-Shell/hamming-numbers.sh

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typeset -a hamming=(1) q2 q3 q5
function nextHamming {
typeset -i h=${hamming[${#hamming[@]}-1]}
q2+=( $(( h*2 )) )
q3+=( $(( h*3 )) )
q5+=( $(( h*5 )) )
h=$( min3 ${q2[0]} ${q3[0]} ${q5[0]} )
(( ${q2[0]} == h )) && ashift q2 >/dev/null
(( ${q3[0]} == h )) && ashift q3 >/dev/null
(( ${q5[0]} == h )) && ashift q5 >/dev/null
hamming+=($h)
}
function ashift {
typeset -n ary=$1
printf '%s\n' "${ary[0]}"
ary=( "${ary[@]:1}" )
}
function min3 {
if (( $1 < $2 )); then
(( $1 < $3 )) && printf '%s\n'$1 || printf '%s\n'$3
else
(( $2 < $3 )) && printf '%s\n'$2 || printf '%s\n'$3
fi
}
for ((i=1; i<=20; i++)); do
nextHamming
printf '%d\t%d\n' "$i" "${hamming[i-1]}"
done
for ((; i<=1690; i++)); do nextHamming; done
nextHamming
printf '%d\t%d\n' "$i" "${hamming[i-1]}"
printf 'elapsed: %s\n' "$SECONDS"