From: phfr24 <phfr24@inf.ufpr.br>
Date: Sun, 24 May 2026 20:19:09 +0000 (-0300)
Subject: add broken prim
X-Git-Url: https://git.wirehaze.ovh/graph-theory.git/commitdiff_plain/HEAD?ds=inline

add broken prim
---

diff --git a/graph/prim.c b/graph/prim.c
new file mode 100644
index 0000000..c74a6dc
--- /dev/null
+++ b/graph/prim.c
@@ -0,0 +1,113 @@
+#include "graph/prim.h"
+#include "graph/search.h"
+#include <errno.h>
+#include <stdlib.h>
+
+/*
+ * todo priority queue, currently its broken
+ * */
+
+static int
+prim_ (struct graph *g, struct graph *pt, struct state *vs, unsigned int ri,
+       unsigned int (*w) (unsigned int, unsigned int))
+{
+  struct squeue sq;
+  struct vertex *r, *n;
+  struct state *rs, *ns;
+  struct edge *e;
+  unsigned int ni;
+  int err;
+
+  if (!(sq.q = calloc (g->nv, sizeof *sq.q)))
+    return -errno;
+
+  sq.f = sq.l = sq.q;
+  *sq.f = &g->v[ri];
+  vs[ri].c = RED;
+
+  while (sq.f <= sq.l)
+    {
+      r = *sq.f;
+      ri = vertex_id (g, r);
+      rs = &vs[ri];
+      e = r->adj;
+
+      while (e && (n = e->to))
+        {
+          ni = vertex_id (g, n);
+          ns = &vs[ni];
+
+          switch (ns->c)
+            {
+            case WHITE:
+              ns->c = RED;
+
+              if ((err = add_arc (pt, ri, ni)))
+                {
+                  free (sq.q);
+                  return err;
+                }
+
+              ns->w = w (ri, ni);
+              ns->from = r;
+
+              *(++sq.l) = n;
+              break;
+
+            case RED:
+              if (ns->w < w (ri, ni))
+                break;
+
+              del_arc (pt, vertex_id (g, ns->from), ni);
+
+              if ((err = add_arc (pt, ri, ni)))
+                {
+                  free (sq.q);
+                  return err;
+                }
+
+              ns->w = w (ri, ni);
+              ns->from = r;
+
+              break;
+            }
+
+          e = e->next;
+        }
+
+      rs->c = BLUE;
+      ++sq.f;
+    }
+
+  free (sq.q);
+  return 0;
+}
+
+struct graph *
+prim (struct graph *g, unsigned int (*w) (unsigned int, unsigned int))
+{
+  struct graph *pt;
+  struct state *vs;
+  unsigned int vi;
+
+  if (!(pt = new_graph (g->nv)))
+    goto err_new_graph;
+
+  if (!(vs = calloc (g->nv, sizeof *vs)))
+    goto err_calloc;
+
+  for (vi = 0; vi < g->nv; ++vi)
+    if (vs[vi].c == WHITE)
+      if (prim_ (g, pt, vs, vi, w))
+        goto err_prim_;
+
+  free (vs);
+  return pt;
+
+err_prim_:
+  free (vs);
+err_calloc:
+  free_graph (pt);
+err_new_graph:
+  return NULL;
+}
diff --git a/graph/prim.h b/graph/prim.h
new file mode 100644
index 0000000..416e46b
--- /dev/null
+++ b/graph/prim.h
@@ -0,0 +1,10 @@
+#ifndef PRIM_H
+#define PRIM_H
+
+#include "graph/adj.h"
+
+/* fixme */
+struct graph *prim (struct graph *g,
+                    unsigned int (*w) (unsigned int, unsigned int));
+
+#endif /* PRIM_H  */
diff --git a/graph/search.h b/graph/search.h
index 738493d..a9a5ab6 100644
--- a/graph/search.h
+++ b/graph/search.h
@@ -10,9 +10,12 @@ enum color
   BLUE
 };
 
+/* lazy */
 struct state
 {
   enum color c;
+  unsigned int w;
+  struct vertex *from;
 };
 
 struct squeue