45 lines
973 B
C++
45 lines
973 B
C++
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#include "algorithm.hpp"
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#include "stm.hpp"
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#include <cmath>
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Algorithm::RationalApproximation Algorithm::BestRationalApproximation(float ratio, uint32_t max_denom) {
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RationalApproximation result;
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uint32_t a = 0, b = 1, c = 1, d = 1;
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while (b + d <= max_denom) {
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auto mediant = (float) (a + c) / (b + d);
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if (ratio == mediant) {
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if (b + d <= max_denom) {
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result.num = a + c;
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result.denom = b + d;
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return result;
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} else if (d > b) {
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result.num = c;
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result.denom = d;
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return result;
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} else {
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result.num = a;
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result.denom = b;
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return result;
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}
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} else if (ratio > mediant) {
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a = a + c;
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b = b + d;
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} else {
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c = a + c;
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d = b + d;
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}
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}
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// check which of the two is the better solution
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float dev_ab = (float) a / b - ratio;
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float dev_cd = (float) c / d - ratio;
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if(fabs(dev_cd) < fabs(dev_ab)) {
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result.num = c;
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result.denom = d;
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} else {
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result.num = a;
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result.denom = b;
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}
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return result;
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}
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