From f0881305402f3dff56f99fcc4cbc8b615581b780 Mon Sep 17 00:00:00 2001
From: Igor Pashev <pashev.igor@gmail.com>
Date: Sun, 28 Aug 2022 15:40:21 +0200
Subject: C, Haskell, Python, Fortran

---
 mendeleev.c | 196 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 196 insertions(+)
 create mode 100644 mendeleev.c

(limited to 'mendeleev.c')

diff --git a/mendeleev.c b/mendeleev.c
new file mode 100644
index 0000000..d90ee23
--- /dev/null
+++ b/mendeleev.c
@@ -0,0 +1,196 @@
+#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;
+}
-- 
cgit v1.2.3