void Hauseholder(int n, double a[nn][nn], double c[nn], double b[nn], int vec, double v[nn][nn])
{
double r=0, s=0, sigma=0, tau=0, a1=0;
if (vec == 1){
    for (int i = 0; i < n; i++){
        for (int j = 0; j < n; j++)
        if (i == j)
            v[i][j] = 1;
        else
            v[i][j] = 0;
    }
}
for (int k = 0; k < n - 2; k++){
    r = fabs(a[k + 1][k]);
    for (int i = k + 1; i < n; i++){
        if (r < fabs(a[i][k])){
            r = fabs(a[i][k]);
        }
    }
    if (r == 0){
        a1 = 0;
    }
    else {
        for (int i = k; i < n; i++){
            a[i][k] = a[i][k] / r;
        }
        s = 0;
        for (int i = k; i < n; i++){
            s = s + a[i][k] * a[i][k];
        }
        sigma = Signf(a[k + 1][k])*pow(s,0.5);
        a[k + 1][k] = a[k + 1][k] + sigma;
        a1 = a[k + 1][k] * sigma;

        for (int j = k; j < n; j++){
            s = 0;
            for (int i = k; i < n; i++){
                s = s + a[i][j] * a[i][k];
            }
            tau = (double)(s / a1);
            for (int i = k; i < n; i++)
                a[i][j] = a[i][j] - tau * a[i][k];
        }

        a[k][k + 1] = -r * sigma;
        for (int j = k + 1; j < n; j++){
            a[k][j] = 0;
        }
        for (int i = k; i < n; i++){
            s = 0;
            for (int j = k; j < n; j++){
                s = s + a[i][j] * a[j][k];
            }
            tau = s / a1;
            for (int j = k; j < n; j++){
                a[i][j] = a[i][j] - tau * a[j][k];
            }
        }
    }
    if (vec == 1){
        for (int i = 0; i < n; i++){
            s = 0;
            for (int j = k; j < n; j++){
                s = s + v[i][j] * a[j][k];
            }
            tau = s / a1;
            for (int j = k; j < n; j++){
                v[i][j] = v[i][j] - tau * a[j][k];
            }
        }
    }
}
b[0] = 0;
for (int i = 0; i < n; i++){
    c[i] = a[i][i];
    if (i <= n - 1)
        b[i + 1] = a[i][i + 1];
}
}