33 lines
833 B
Nim
33 lines
833 B
Nim
import sets, strutils, algorithm
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proc primes(n: int64): seq[int64] =
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var multiples: HashSet[int64]
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for i in 2..n:
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if i notin multiples:
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result.add i
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for j in countup(i*i, n, i.int):
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multiples.incl j
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proc truncatablePrime(n: int64): tuple[left, right: int64] =
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var
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primelist: seq[string]
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for x in primes(n):
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primelist.add($x)
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reverse primelist
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var primeset = primelist.toHashSet
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for n in primelist:
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var alltruncs: HashSet[string]
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for i in 0..n.high:
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alltruncs.incl n[i..n.high]
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if alltruncs <= primeset:
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result.left = parseInt(n)
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break
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for n in primelist:
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var alltruncs: HashSet[string]
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for i in 0..n.high:
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alltruncs.incl n[0..i]
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if alltruncs <= primeset:
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result.right = parseInt(n)
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break
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echo truncatablePrime(1000000i64)
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