24 lines
465 B
C
24 lines
465 B
C
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/*
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* http://projecteuler.net
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*
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* Projecteuler - Problem 25
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* -----------------------
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* 2010-07-13 Henrik Hautakoski
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*
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* Alot of math, binet's formula
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*/
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#include <math.h>
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#include <stdio.h>
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#define LOG10PHI 0.20898764024997876221 /* log10((1+sqrt(5))/2) */
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#define MAGIC 0.65051499783199062676 /* |(log10(5) / 2) - 1| */
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#define fibolen(n) ((int) ceil(((n) - MAGIC) / LOG10PHI))
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int main() {
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printf("%i\n", fibolen(1000));
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return 0;
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}
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