faster way to delete the first node

diff --git a/kavl.h b/kavl.h
index 3155cc360ff99483501f64a914129f0f0ae3994b..a1c40f3865730245cdb11a07bc339466c5c9035d 100644 (file)
--- a/kavl.h
+++ b/kavl.h
@@ -182,12 +182,18 @@ int main(void) {
                unsigned char dir[KAVL_MAX_DEPTH]; \
                int i, d = 0, cmp; \
                fake.__head.p[0] = *root_, fake.__head.p[1] = 0; \
-               for (cmp = -1, p = &fake; cmp; cmp = __cmp(x, p)) { \
-                       int which = (cmp > 0); \
-                       dir[d] = which; \
-                       path[d++] = p; \
-                       p = p->__head.p[which]; \
-                       if (p == 0) return 0; \
+               if (x) { \
+                       for (cmp = -1, p = &fake; cmp; cmp = __cmp(x, p)) { \
+                               int which = (cmp > 0); \
+                               dir[d] = which; \
+                               path[d++] = p; \
+                               p = p->__head.p[which]; \
+                               if (p == 0) return 0; \
+                       } \
+               } else { \
+                       for (p = &fake; p; p = p->__head.p[0]) \
+                               dir[d] = 0, path[d++] = p; \
+                       p = path[--d]; \
                } \
                for (i = 1; i < d; ++i) --path[i]->__head.size; \
                if (p->__head.p[1] == 0) { /* ((1,.)2,3)4 => (1,3)4; p=2 */ \
@@ -314,11 +320,12 @@ int main(void) {
  *
  * @param suf     name suffix used in KAVL_INIT()
  * @param proot   pointer to the root of the tree (in/out: root may change)
- * @param x       node value to delete (in)
+ * @param x       node value to delete; if NULL, delete the first node (in)
  *
  * @return node removed from the tree if present, or NULL if absent
  */
 #define kavl_erase(suf, proot, x) kavl_erase_##suf(proot, x)
+#define kavl_erase_first(suf, proot) kavl_erase_##suf(proot, 0)
 
 #define kavl_itr_t(suf) struct kavl_itr_##suf
 #define kavl_itr_first(suf, root, itr) kavl_itr_first_##suf(root, itr)