68 lines
940 B
C
68 lines
940 B
C
#include "solve.h"
|
|
|
|
#include <math.h>
|
|
#include <float.h>
|
|
|
|
#define MAX_ITER 30
|
|
|
|
int t12_solve (
|
|
double (*xt) (double),
|
|
double (*yt) (double),
|
|
double a, double b,
|
|
double eps, double *res
|
|
) {
|
|
int it;
|
|
|
|
double xa = xt(a), ya = yt(a);
|
|
double xb = xt(b), yb = yt(b);
|
|
double xl = xa, yl = yb;
|
|
|
|
int n = 2;
|
|
double h = (b - a) * 0.5;
|
|
double x = xb - xl;
|
|
double y = yb - yl;
|
|
double len_n = sqrt(x * x + y * y);
|
|
|
|
for (it = 1; it <= MAX_ITER; ++it)
|
|
{
|
|
double tn = a + h;
|
|
double len_2n = 0;
|
|
|
|
for (int i = 1; i < n; i++)
|
|
{
|
|
double xc = xt(tn);
|
|
double yc = yt(tn);
|
|
|
|
x = xc - xl;
|
|
y = yc - yl;
|
|
len_2n += sqrt(x * x + y * y);
|
|
|
|
xl = xc;
|
|
yl = yc;
|
|
tn += h;
|
|
}
|
|
|
|
x = xb - xl;
|
|
y = yb - yl;
|
|
len_2n += sqrt(x * x + y * y);
|
|
|
|
h *= 0.5;
|
|
|
|
if (fabs(len_2n - len_n) < eps)
|
|
break;
|
|
|
|
xl = xa;
|
|
yl = ya;
|
|
|
|
len_n = len_2n;
|
|
n <<= 1;
|
|
}
|
|
|
|
if (it > MAX_ITER)
|
|
return -1;
|
|
|
|
*res = len_n;
|
|
|
|
return n;
|
|
}
|
|
|