54 lines
1.3 KiB
Julia
54 lines
1.3 KiB
Julia
#=
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Created on 07 Sep 2021
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@author: David Doblas Jiménez
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@email: daviddoji@pm.me
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Solution for Problem 37 of Project Euler
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https://projecteuler.net/problem=37
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=#
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using BenchmarkTools
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using Primes
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function is_truncatable_prime(number)
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num_str_rev = reverse(digits(number))
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for (idx,num) in enumerate(join(num_str_rev))
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if !isprime(parse(Int, join(num_str_rev[idx:end]))) ||
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!isprime(parse(Int, join(num_str_rev[1:end-idx+1])))
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return false
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end
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end
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return true
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end
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function Problem37()
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"""
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The number 3797 has an interesting property. Being prime itself, it is
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possible to continuously remove digits from left to right, and remain
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prime at each stage: 3797, 797, 97, and 7.
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Similarly we can work from right to left: 3797, 379, 37, and 3.
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Find the sum of the only eleven primes that are both truncatable from left
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to right and right to left.
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NOTE: 2, 3, 5, and 7 are not considered to be truncatable primes.
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"""
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ans = 0
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# Statement of the problem says this
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primes_list = primes(11, 1_000_000)
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for num in primes_list
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if is_truncatable_prime(num)
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ans += num
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end
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end
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return ans
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end
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println("Time to evaluate Problem 37:")
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@btime Problem37()
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println("")
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println("Result for Problem 37: ", Problem37())
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