```/* nag_mesh_dim2_renumber (d06ccc) Example Program.
*
* Copyright 2019 Numerical Algorithms Group.
*
* Mark 27.0, 2019.
*/

#include <stdio.h>
#include <nag.h>

#define EDGE(I, J) edge[3*((J) -1)+(I) -1]
#define CONN(I, J) conn[3*((J) -1)+(I) -1]
#define COOR(I, J) coor[2*((J) -1)+(I) -1]

int main(void)
{
Integer exit_status, i, itrace, nedge, nelt, nnz, nnzmax, nv, reftk;
NagError fail;
char pmesh[2];
double *coor = 0;
Integer *conn = 0, *edge = 0, *icol = 0, *irow = 0;

INIT_FAIL(fail);

exit_status = 0;

printf(" nag_mesh_dim2_renumber (d06ccc) Example Program Results\n\n");
fflush(stdout);

/* Skip heading in data file */
scanf("%*[^\n] ");

/* Reading of the geometry */
scanf("%" NAG_IFMT "", &nv);
scanf("%" NAG_IFMT "", &nelt);
scanf("%" NAG_IFMT "", &nedge);
scanf("%*[^\n] ");

nnzmax = 10 * nv;

/* Allocate memory */

if (!(coor = NAG_ALLOC(2 * nv, double)) ||
!(conn = NAG_ALLOC(3 * nelt, Integer)) ||
!(edge = NAG_ALLOC(3 * nedge, Integer)) ||
!(irow = NAG_ALLOC(nnzmax, Integer)) ||
!(icol = NAG_ALLOC(nnzmax, Integer)))
{
printf("Allocation failure\n");
exit_status = -1;
goto END;
}

for (i = 1; i <= nv; ++i) {
scanf("%lf", &COOR(1, i));
scanf("%lf", &COOR(2, i));
scanf("%*[^\n] ");
}

for (i = 1; i <= nelt; ++i) {
scanf("%" NAG_IFMT "", &CONN(1, i));
scanf("%" NAG_IFMT "", &CONN(2, i));
scanf("%" NAG_IFMT "", &CONN(3, i));
scanf("%" NAG_IFMT "", &reftk);
scanf("%*[^\n] ");
}

for (i = 1; i <= nedge; ++i) {
scanf("%" NAG_IFMT "", &reftk);
scanf("%" NAG_IFMT "", &EDGE(1, i));
scanf("%" NAG_IFMT "", &EDGE(2, i));
scanf("%" NAG_IFMT "", &EDGE(3, i));
scanf("%*[^\n] ");
}
scanf(" ' %1s '", pmesh);
scanf("%*[^\n] ");

/* Compute the sparsity of the FE matrix */
/* from the input geometry */

/* nag_mesh_dim2_sparsity (d06cbc).
* Generates a sparsity pattern of a Finite Element matrix
* associated with a given mesh
*/
nag_mesh_dim2_sparsity(nv, nelt, nnzmax, conn, &nnz, irow, icol, &fail);

if (fail.code == NE_NOERROR) {
if (pmesh[0] == 'N') {
printf(" The Matrix Sparsity characteristics\n");
printf(" before the renumbering\n");
printf(" nv  =%6" NAG_IFMT "\n", nv);
printf(" nnz =%6" NAG_IFMT "\n", nnz);
}
else if (pmesh[0] == 'Y') {
/* Output the sparsity of the mesh to view */
/* it using the NAG Graphics Library */

printf(" %10" NAG_IFMT "%10" NAG_IFMT "\n", nv, nnz);

for (i = 0; i < nnz; ++i)
printf(" %10" NAG_IFMT "%10" NAG_IFMT "\n", irow[i], icol[i]);
}
else {
printf("Problem with the printing option Y or N\n");
exit_status = -1;
goto END;
}
}
else {
printf("Error from nag_mesh_dim2_sparsity (d06cbc).\n%s\n", fail.message);
exit_status = 1;
goto END;
}

/* Call the renumbering routine and get the new sparsity */

itrace = 1;

/* nag_mesh_dim2_renumber (d06ccc).
* Renumbers a given mesh using Gibbs method
*/
fflush(stdout);
nag_mesh_dim2_renumber(nv, nelt, nedge, nnzmax, &nnz, coor, edge, conn, irow,
icol, itrace, 0, &fail);
if (fail.code == NE_NOERROR) {
if (pmesh[0] == 'N') {
printf("\n The Matrix Sparsity characteristics\n");
printf(" after the renumbering\n");
printf(" nv   =%6" NAG_IFMT "\n", nv);
printf(" nnz  =%6" NAG_IFMT "\n", nnz);
printf(" nelt =%6" NAG_IFMT "\n", nelt);
}
else if (pmesh[0] == 'Y') {
/* Output the sparsity of the renumbered mesh */
/* to view it using the NAG Graphics Library */

printf("%10" NAG_IFMT "%10" NAG_IFMT "\n", nv, nnz);

for (i = 0; i < nnz; ++i)
printf(" %10" NAG_IFMT "%10" NAG_IFMT "\n", irow[i], icol[i]);

/* Output the renumbered mesh to view */
/* it using the NAG Graphics Library */

printf(" %10" NAG_IFMT "%10" NAG_IFMT "\n", nv, nelt);

for (i = 1; i <= nv; ++i)
printf("  %15.6e  %15.6e  \n", COOR(1, i), COOR(2, i));

reftk = 0;
for (i = 1; i <= nelt; ++i)
printf(" %10" NAG_IFMT "%10" NAG_IFMT "%10" NAG_IFMT "%10" NAG_IFMT
"\n", CONN(1, i), CONN(2, i), CONN(3, i), reftk);
}
}
else {
printf("Error from nag_mesh_dim2_renumber (d06ccc).\n%s\n", fail.message);
exit_status = 1;
goto END;
}

END:
NAG_FREE(coor);
NAG_FREE(conn);
NAG_FREE(edge);
NAG_FREE(irow);
NAG_FREE(icol);

return exit_status;
}
```