Molas acopladas (matriz tridiagonal) II

#include <stdio.h>
#include <math.h>

/*
Matriz tridiagonal da forma:
d a 0 0 0 0       x       B
b d a 0 0 0       x       B
0 b d a 0 0   *   x   =   B
0 0 b d a 0       x       B
0 0 0 b d a       x       B
0 0 0 0 b d       x       B
*/

/*
V = [1 2 3 4 5 6 7 8 9 10]
dVdx = V(i+1) - V(i)

-1  1   0   0  0     1         1
 0 -1   1   0  0     2         1
 0  0  -1   1  0  *  3     =   1
 0  0   0  -1  1     4         1
 0  0   0   0 -1     5         1

dv = f(x) <=> A * v = f(x)
*/

#define n 250
#define C 1
#define K 6
#define m 1
#define omega 0.1
#define alpha (2*K - m*omega*omega)

int main(void)
{
    double a[n], b[n], B[n], x[n], d[n];

    for (int i = 0; i < n; ++i)
    {
        b[i] = -K;
        a[i] = -K;
        d[i] = alpha;
    }

    d[0] -= K;
    d[n-1] -= K;

    a[0] /= d[0];
    B[0] /= d[0];

    for (int i = 1; i < n; ++i)
    {
        a[i] /= d[i] - b[i]*a[i-1];
        B[i] = (B[i] - b[i]*B[i-1])/(d[i] - b[i]*a[i-1]);
    }

    B[n] = (B[n] - b[n]*B[n-1])/(d[n] - b[n]*a[n-1]);

    x[0] = B[0];

    for (int i = n-1; i >= 1; --i)
    {
        x[n] = B[n];
        x[i] = B[i] - a[i]*x[i+1];
    }

    for (int i = 0; i < n; ++i)
    {
        printf("%d %lf\n", i, x[i]);
    }

    return 0;
}