Recaman's sequence: Difference between revisions

=={{header|Nim}}==

<lang Nim>import sequtils, sets, strutils

iterator recaman(num: Positive = Natural.high): tuple[n, a: int; duplicate: bool] =

var a = 0

yield (0, a, false)

var known = [0].toHashSet

for n in 1..<num:

var next = a - n

if next <= 0 or next in known:

next = a + n

a = next

yield (n, a, a in known)

known.incl a

echo "First 15 numbers in Recaman’s sequence: ", toSeq(recaman(15)).mapIt(it.a).join(" ")

for (n, a, dup) in recaman():

if dup:

echo "First duplicate found: a($1) = $2".format(n, a)

break

var target = toSeq(0..1000).toHashSet

for (n, a, dup) in recaman():

target.excl a

if target.card == 0:

echo "All numbers from 0 to 1000 generated after $1 terms.".format(n)

break</lang>

{{out}}

<pre>First 15 numbers in Recaman’s sequence: 0 1 3 6 2 7 13 20 12 21 11 22 10 23 9

First duplicate found: a(24) = 42

All numbers from 0 to 1000 generated after 328002 terms.</pre>