Hailstone sequence: Difference between revisions
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start sequence
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</pre>
=={{header|S-BASIC}}==
<lang s-basic>comment
Compute and display "hailstone" (i.e., Collatz) sequence
for a given number and find the longest sequence in the
range permitted by S-BASIC's 16-bit integer data type.
end
$lines
$constant false = 0
$constant true = FFFFH
rem - compute p mod q
function mod(p, q = integer) = integer
end = p - q * (p/q)
comment
Compute, and optionally display, hailstone sequence for n.
Return length of sequence or zero on overflow
end
function hailstone(n, display = integer) = integer
var length = integer
length = 1
while (n <> 1) and (n > 0) do
begin
if display then print using "##### ", n;
if mod(n,2) = 0 then
n = n / 2
else
n = (n * 3) + 1
length = length + 1
end
if display then print using "##### ", n
rem - return 0 on overflow
if n < 0 then length = 0
end = length
var n, limit, slen, longest, n_longest = integer
input "Display hailstone sequence for what number"; n
slen = hailstone(n, true)
print "Sequence length = "; slen
rem - find longest sequence before overflow
n = 2
longest = 1
slen = 1
limit = 1000;
print "Searching for longest sequence up to N =", limit," ..."
while (n < limit) and (slen <> 0) do
begin
slen = hailstone(n, false)
if slen > longest then
begin
longest = slen
n_longest = n
end
n = n + 1
end
if slen = 0 then print "Search terminated with overflow at";n-1
print "Maximum sequence length =";longest;" for N =";n_longest
end
</lang>
{{out}}
<pre>Display hailstone sequence for what number? 27
27 82 41 124 62 31 94 47 142 71
214 107 322 161 484 242 121 364 182 91
274 137 412 206 103 310 155 466 233 700
350 175 526 263 790 395 1186 593 1780 890
445 1336 668 334 167 502 251 754 377 1132
566 283 850 425 1276 638 319 958 479 1438
719 2158 1079 3238 1619 4858 2429 7288 3644 1822
911 2734 1367 4102 2051 6154 3077 9232 4616 2308
1154 577 1732 866 433 1300 650 325 976 488
244 122 61 184 92 46 23 70 35 106
53 160 80 40 20 10 5 16 8 4
2 1
Sequence length = 112
Searching for longest sequence up to N = 1000 ...
Search terminated with overflow at 447
Maximum sequence length = 144 for N = 327
</pre>
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