28 lines
No EOL
549 B
C++
28 lines
No EOL
549 B
C++
#include "special_sum.h"
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size_t gauss_sum(size_t n)
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{
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return (n*(n+1))/2;
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}
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size_t special_sum_loop(size_t n)
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{
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size_t sum = 0;
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for (size_t i = 1; i < n+1; ++i)
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{
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if (i % 3 == 0 || i % 5 == 0)
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{
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sum += i;
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}
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}
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return sum;
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}
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size_t special_sum_noloop(size_t n)
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{
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size_t factor_3 = gauss_sum(n/3); // dividing int by int automatically gets rounded off
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size_t factor_5 = gauss_sum(n/5);
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size_t factor_15 = gauss_sum(n/15);
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return factor_3*3 + factor_5*5 - factor_15*15;
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} |