Truncatable primes: Difference between revisions
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739399 is the largest right truncatable prime <= 1000000.
</lang>
=={{header|Nimrod}}==
{{trans|Python}}
<lang nimrod>import sets, strutils, algorithm
proc primes(n): seq[int] =
result = @[]
var multiples = initSet[int]()
for i in 2..n:
if i notin multiples:
result.add i
for j in countup(i*i, n, i):
multiples.incl j
proc truncatablePrime(n): tuple[left: int, right: int] =
var
primelist: seq[string] = @[]
for x in primes(n):
primelist.add($x)
reverse primelist
var primeset = toSet primelist
for n in primelist:
var alltruncs = initSet[string]()
for i in 0..n.len:
alltruncs.incl n[1..n.high]
if alltruncs <= primeset:
result.left = parseInt(n)
break
for n in primelist:
var alltruncs = initSet[string]()
for i in 0..n.len:
alltruncs.incl n[0..i]
if alltruncs <= primeset:
result.right = parseInt(n)
break
echo truncatablePrime(1000000)</lang>
Output:
<pre>(left: 999961, right: 739399)</pre>
=={{header|ooRexx}}==
<lang ooRexx>
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