43 lines
1.0 KiB
Factor
43 lines
1.0 KiB
Factor
! Copyright (c) 2007 Aaron Schaefer.
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! See http://factorcode.org/license.txt for BSD license.
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USING: kernel math project-euler.common ;
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IN: project-euler.012
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! http://projecteuler.net/index.php?section=problems&id=12
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! DESCRIPTION
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! -----------
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! The sequence of triangle numbers is generated by adding the natural numbers.
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! So the 7th triangle number would be 1 + 2 + 3 + 4 + 5 + 6 + 7 = 28. The first
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! ten terms would be:
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! 1, 3, 6, 10, 15, 21, 28, 36, 45, 55, ...
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! Let us list the factors of the first seven triangle numbers:
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! 1: 1
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! 3: 1,3
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! 6: 1,2,3,6
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! 10: 1,2,5,10
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! 15: 1,3,5,15
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! 21: 1,3,7,21
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! 28: 1,2,4,7,14,28
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! We can see that the 7th triangle number, 28, is the first triangle number to
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! have over five divisors.
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! Which is the first triangle number to have over five-hundred divisors?
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! SOLUTION
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! --------
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: euler012 ( -- answer )
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8 [ dup nth-triangle tau* 500 < ] [ 1 + ] while nth-triangle ;
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! [ euler012 ] 10 ave-time
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! 6573 ms ave run time - 346.27 SD (10 trials)
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SOLUTION: euler012
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