tridag.cpp

追赶法解线性方程组

void tridag(double a[],double b[], double c[],double r[], double u[], int n)
{ 
    const int nmax = 100;
    double gam[100];
    if (b[1] == 0.0)
	{
		return;
	}
    double bet = b[1];
    u[1] = r[1] / bet;
    for (int j = 2; j<=n; j++)
	{
        gam[j] = c[j - 1] / bet;
        bet = b[j] - a[j] * gam[j];
        if (bet == 0.0)
		{
			return;
		}
        u[j] = (r[j] - a[j] * u[j - 1]) / bet;
    }
    for (j = n - 1; j>=1; j--)
	{
        u[j] = u[j] - gam[j + 1] * u[j + 1];
    }
}