Hailstone sequence: Difference between revisions
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</pre>
=={{header|ABC}}==
<syntaxhighlight lang="abc">HOW TO RETURN hailstone n:
PUT {} IN seq
WHILE 1=1:
PUT n IN seq[#seq]
SELECT:
n=1: RETURN seq
n mod 2=0: PUT floor(n/2) IN n
n mod 2=1: PUT 3*n+1 IN n
RETURN seq
PUT hailstone 27 IN h27
WRITE "Length of Hailstone sequence for 27:", #h27/
WRITE "First 4 elements:", h27[0], h27[1], h27[2], h27[3]/
WRITE "Last 4 elements:", h27[#h27-4], h27[#h27-3], h27[#h27-2], h27[#h27-1]/
PUT 0, 0 IN longest, length
FOR n IN {1..100000}:
PUT hailstone n IN hn
IF #hn > length:
PUT n, #hn IN longest, length
WRITE longest, "has the longest hailstone sequence < 100,000, of length:", length/</syntaxhighlight>
{{out}}
<pre>Length of Hailstone sequence for 27: 112
First 4 elements: 27 82 41 124
Last 4 elements: 8 4 2 1
77031 has the longest hailstone sequence < 100,000, of length: 351</pre>
=={{header|ACL2}}==
<syntaxhighlight lang="lisp">(defun hailstone (len)
Line 6,009 ⟶ 6,037:
<syntaxhighlight lang="kotlin">
fun hailstone(start: Int) = generateSequence(start) { n ->
when {
if (n == 1) null else if (n % 2 == 0) n / 2 else n * 3 + 1▼
n == 1 -> null
n % 2 == 0 -> n / 2
}
}
Line 6,015 ⟶ 6,047:
val hail27 = hailstone(27).toList()
println("The hailstone sequence for 27 has ${hail27.size} elements:\n$hail27")
val (n, length) = (1..100000).asSequence()
.map { it to hailstone(it).count() }
.maxBy { it.second }
println("The number between 1 and 100000 with the longest hailstone sequence is $n, of length $length")
}
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