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#include<ctype.h>
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
static const char *const ELEMENTS[] = { "?",
"Ac", "Ag", "Al", "Am", "Ar", "As", "At", "Au", "B", "Ba", "Be", "Bh",
"Bi", "Bk", "Br", "C", "Ca", "Cd", "Ce", "Cf", "Cl", "Cm", "Cn", "Co",
"Cr", "Cs", "Cu", "Db", "Ds", "Dy", "Er", "Es", "Eu", "F", "Fe", "Fl",
"Fm", "Fr", "Ga", "Gd", "Ge", "H", "He", "Hf", "Hg", "Ho", "Hs", "I",
"In", "Ir", "K", "Kr", "La", "Li", "Lr", "Lu", "Lv", "Mc", "Md", "Mg",
"Mn", "Mo", "Mt", "N", "Na", "Nb", "Nd", "Ne", "Nh", "Ni", "No", "Np",
"O", "Og", "Os", "P", "Pa", "Pb", "Pd", "Pm", "Po", "Pr", "Pt", "Pu",
"Ra", "Rb", "Re", "Rf", "Rg", "Rh", "Rn", "Ru", "S", "Sb", "Sc", "Se",
"Sg", "Si", "Sm", "Sn", "Sr", "Ta", "Tb", "Tc", "Te", "Th", "Ti", "Tl",
"Tm", "Ts", "U", "V", "W", "Xe", "Y", "Yb", "Zn", "Zr"
};
static const size_t NELEMENTS = sizeof (ELEMENTS) / sizeof (const char *) - 1;
typedef struct formula
{
const char *tail;
size_t n;
size_t *els;
struct formula *next;
} formula_t;
static void
search (size_t *start, size_t *len, size_t shift, char c)
{
size_t l, m, u;
int c_ = tolower (c);
u = *start + *len;
l = *start;
while (l < u)
{
m = (l + u) / 2;
if (tolower (ELEMENTS[m][shift]) < c_)
l = m + 1;
else
u = m;
}
if ((l == *start + *len) || (tolower (ELEMENTS[l][shift]) != c_))
{
*len = 0;
return;
}
u = *start + *len;
*start = l;
while (l < u)
{
m = (l + u) / 2;
if (c_ < tolower (ELEMENTS[m][shift]))
u = m;
else
l = m + 1;
}
*len = u - *start;
}
static formula_t *
new_formula (const char *tail, size_t n, const size_t *els)
{
formula_t *f = (formula_t *) malloc (sizeof (formula_t));
if (!f)
return NULL;
f->els = (size_t *) malloc (sizeof (*f->els) * (n + strlen (tail)));
if (!f->els)
{
free (f);
return NULL;
}
if (n > 0)
(void) memcpy (f->els, els, n * sizeof (*f->els));
f->n = n;
f->tail = tail;
f->next = NULL;
return f;
}
static void
free_formula (formula_t * f)
{
while (f)
{
formula_t *next = f->next;
if (f->els)
free (f->els);
free (f);
f = next;
}
}
static void
advance (formula_t * f)
{
const char *tail = f->tail;
size_t n = f->n;
size_t start = 1;
size_t len = NELEMENTS;
size_t shift = 0;
while (tail[shift])
{
search (&start, &len, shift, tail[shift]);
if (!len)
break;
shift++;
if (!ELEMENTS[start][shift])
{
if (n != f->n)
{
formula_t *g = new_formula (tail, n, f->els);
if (!g)
break;
g->next = f->next;
f->next = g;
f = g;
}
f->els[f->n++] = start;
f->tail = &tail[shift];
start++;
len--;
}
}
if (n == f->n)
{
f->els[f->n++] = 0;
f->tail += 1;
}
}
static formula_t *
explode (const char *word)
{
formula_t *formula = new_formula (word, 0, NULL);
if (!formula)
return NULL;
while (*word)
{
word = NULL;
formula_t *f = formula;
while (f)
{
if (*f->tail)
{
advance (f);
if (!word)
word = f->tail;
}
f = f->next;
}
}
return formula;
}
int
main (int argc, const char *argv[])
{
for (int w = 1; w < argc; w++)
{
const char *word = argv[w];
printf ("%s:\n", word);
formula_t *formula = explode (word);
if (!formula)
return EXIT_FAILURE;
for (formula_t * f = formula; f; f = f->next)
{
for (size_t i = 0; i < f->n; i++)
printf (" %s", ELEMENTS[f->els[i]]);
if (f->n)
printf ("\n");
}
free_formula (formula);
}
return EXIT_SUCCESS;
}
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