Recaman's sequence: Difference between revisions

=={{header|CLU}}==

<lang clu>% Recaman sequence

recaman = cluster is new, fetch

rep = array[int]

new = proc () returns (cvt)

a: rep := rep$predict(0,1000000)

rep$addh(a,0)

return(a)

end new

% Find the N'th element of the Recaman sequence

fetch = proc (a: cvt, n: int) returns (int)

if n > rep$high(a) then extend(a,n) end

return(a[n])

end fetch

% See if N has already been generated

prev = proc (a: rep, n: int) returns (bool)

for el: int in rep$elements(a) do

if el = n then return(true) end

end

return(false)

end prev

% Generate members of the sequence until 'top' is reached

extend = proc (a: rep, top: int)

while rep$high(a) < top do

n: int := rep$high(a) + 1

sub: int := a[n-1] - n

add: int := a[n-1] + n

if sub>0 cand ~prev(a, sub)

then rep$addh(a, sub)

else rep$addh(a, add)

end

end

end extend

end recaman

start_up = proc ()

po: stream := stream$primary_output()

A: recaman := recaman$new()

% Print the first 15 members

stream$puts(po, "First 15 items:")

for i: int in int$from_to(0, 14) do

stream$puts(po, " " || int$unparse(A[i]))

end

% Find the first duplicated number

begin

i: int := 0

while true do

i := i + 1

for j: int in int$from_to(0, i-1) do

if A[i]=A[j] then exit found(i, A[i]) end

end

end

end except when found(i, n: int):

stream$putl(po, "\nFirst duplicated number: A("

|| int$unparse(i) || ") = " || int$unparse(n))

end

% Find the amount of terms needed to generate all integers 0..1000

begin

seen: array[bool] := array[bool]$fill(0,1001,false)

left: int := 1001

n: int := -1

while left > 0 do

n := n + 1

if A[n] <= 1000 cand ~seen[A[n]] then

left := left - 1

seen[A[n]] := true

end

end

stream$putl(po, "Terms needed to generate [0..1000]: "

|| int$unparse(n))

end

end start_up</lang>

{{out}}

<pre>First 15 items: 0 1 3 6 2 7 13 20 12 21 11 22 10 23 9

First duplicated number: A(24) = 42

Terms needed to generate [0..1000]: 328002</pre>