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https://github.com/TheAlgorithms/Ruby
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40 lines
No EOL
1 KiB
Ruby
40 lines
No EOL
1 KiB
Ruby
#Project Euler Problem 7: https://projecteuler.net/problem=7
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#10001st prime
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#By listing the first six prime numbers: 2, 3, 5, 7, 11, and 13, we
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#can see that the 6th prime is 13.
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#What is the 10001st prime number?
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#References: https://en.wikipedia.org/wiki/Prime_number
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def is_prime?(number)
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value = true
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if number > 1 and number < 4
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# 2 and 3 are primes
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value = true
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elsif number < 2 or number % 2 == 0 or number % 3 == 0
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# Negatives, 0, 1, all even numbers, all multiples of 3 are not primes
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value = false
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end
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end_range = (Math.sqrt(number) + 1).to_i
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# All primes number are in format of 6k +/- 1
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for i in (5..end_range).step(6)
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if number % i == 0 or number % (i + 2) == 0
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value = false
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end
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end
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result = value
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end
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def solution(nth = 10001)
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primes = Array.new()
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num = 2
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while primes.length < nth
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if is_prime?(num)
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primes.append(num)
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end
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num += 1
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end
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primes[primes.length - 1]
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end
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answer = solution()
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p answer |