54 lines
740 B
C
54 lines
740 B
C
#include "solve.h"
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#include <math.h>
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#include <float.h>
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#define MAX_ITER 30
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int t12_solve (
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double (*xt) (double),
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double (*yt) (double),
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double a, double b,
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double eps, double *res
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) {
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int it;
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int n = 1;
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double h = (b - a) * 0.5;
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double x = xt(b) - xt(a);
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double y = yt(b) - yt(a);
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double len_n = sqrt(x * x + y * y);
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for (it = 1; it <= MAX_ITER; ++it)
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{
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double t = a;
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double tn = a + h;
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double len_2n = 0;
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for (int i = 0; i < n; i++)
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{
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x = xt(tn) - xt(t);
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y = yt(tn) - yt(t);
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len_2n += sqrt(x * x + y * y);
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t = tn;
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tn += h;
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}
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h *= 0.5;
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if (fabs(len_2n - len_n) < eps)
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break;
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len_n = len_2n;
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n <<= 1;
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}
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if (it > MAX_ITER)
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return -1;
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*res = len_n;
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return n;
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}
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