```/* nag_lapacklin_zgtcon (f07cuc) Example Program.
*
* Copyright 2020 Numerical Algorithms Group.
*
* Mark 27.1, 2020.
*
*/
#include <math.h>
#include <nag.h>
#include <stdio.h>

int main(void) {
/* Scalars */
double anorm, rcond;
Integer exit_status = 0, i, n;

/* Arrays */
Complex *d = 0, *dl = 0, *du = 0, *du2 = 0;
Integer *ipiv = 0;

/* Nag Types */
NagError fail;

#define CABS(dl) sqrt(dl.re *dl.re + dl.im * dl.im)

INIT_FAIL(fail);

printf("nag_lapacklin_zgtcon (f07cuc) Example Program Results\n\n");
/* Skip heading in data file */
scanf("%*[^\n]");
scanf("%" NAG_IFMT "%*[^\n]", &n);
if (n < 0) {
printf("Invalid n\n");
exit_status = -2;
goto END;
}
/* Allocate memory */
if (!(d = NAG_ALLOC(n, Complex)) || !(dl = NAG_ALLOC(n - 1, Complex)) ||
!(du = NAG_ALLOC(n - 1, Complex)) || !(du2 = NAG_ALLOC(n - 2, Complex)) ||
!(ipiv = NAG_ALLOC(n, Integer))) {
printf("Allocation failure\n");
exit_status = -1;
goto END;
}

/* Read the tridiagonal matrix A from data file */
for (i = 0; i < n - 1; ++i)
scanf(" ( %lf , %lf )", &du[i].re, &du[i].im);
scanf("%*[^\n]");
for (i = 0; i < n; ++i)
scanf(" ( %lf , %lf )", &d[i].re, &d[i].im);
scanf("%*[^\n]");
for (i = 0; i < n - 1; ++i)
scanf(" ( %lf , %lf )", &dl[i].re, &dl[i].im);
scanf("%*[^\n]");

/* Compute the 1-norm of A */

if (n == 1) {
anorm = CABS(d[0]);
} else {
anorm = MAX(CABS(d[0]) + CABS(dl[0]), CABS(d[n - 1]) + CABS(du[n - 2]));
for (i = 1; i < n - 1; ++i)
anorm = MAX(anorm, CABS(d[i]) + CABS(dl[i]) + CABS(du[i - 1]));
}
/* nag_lapacklin_zgttrf (f07crc)
* LU factorization of complex tridiagonal matrix A
*/
nag_lapacklin_zgttrf(n, dl, d, du, du2, ipiv, &fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_lapacklin_zgttrf (f07crc).\n%s\n", fail.message);
exit_status = 1;
goto END;
}

/* Estimate the condition number of A using
* nag_lapacklin_zgtcon (f07cuc).
* Estimates the reciprocal of the condition number of a LU factorized
* complex tridiagonal matrix.
*/
nag_lapacklin_zgtcon(Nag_OneNorm, n, dl, d, du, du2, ipiv, anorm, &rcond,
&fail);
if (fail.code != NE_NOERROR) {
printf("Error from nag_lapacklin_zgtcon (f07cuc).\n%s\n", fail.message);
exit_status = 2;
goto END;
}

/* Print the estimated condition number */
if (rcond >= nag_machine_precision)
printf("Estimate of condition number = %11.2e\n\n", 1.0 / rcond);
else
printf("A is singular to working precision. RCOND = %11.2e\n\n", rcond);
END:
NAG_FREE(d);
NAG_FREE(dl);
NAG_FREE(du);
NAG_FREE(du2);
NAG_FREE(ipiv);

return exit_status;
}
```