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35 lines
835 B
Ruby
35 lines
835 B
Ruby
#Project Euler Problem 6: #https://projecteuler.net/problem=6
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#Sum square difference
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#The sum of the squares of the first ten natural numbers #is,
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# 1^2 + 2^2 + ... + 10^2 = 385
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#The square of the sum of the first ten natural numbers #is,
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# (1 + 2 + ... + 10)^2 = 55^2 = 3025
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#Hence the difference between the sum of the squares of #the first ten
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#natural numbers and the square of the sum is 3025 - 385 = 2640.
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#Find the difference between the sum of the squares of the first one
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#hundred natural numbers and the square of the sum.
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def solution?(num)
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x = 1
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y = 1
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result = 1
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gap = 3
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while y < num
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x += gap
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gap += 2
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y += 1
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result += x
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end
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r_n_pow2_plus_n_pow2 = result
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r_sum_n_pow2 = (((num / 2) + 0.5) * num) ** 2
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r_sum_n_pow2 - r_n_pow2_plus_n_pow2
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end
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answer = 0
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answer = solution?(10)
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p answer
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