fix(tree): fix wrong rotation function

src/tree/vieter_tree_balancing.c

@@ -21,8 +21,12 @@ bool vieter_tree_node_validate(vieter_tree_node *node,
         vieter_tree_node_get(node->children[0], vieter_tree_node_black)) &&
        (node->children[1] == NULL ||
         vieter_tree_node_get(node->children[1], vieter_tree_node_black)));
+  bool right_child_flag_set =
+      node->parent == NULL ||
+      (vieter_tree_node_get(node, vieter_tree_node_right) ==
+       (node->parent->children[1] == node));
 
-  return correctly_colored_children &&
+  return correctly_colored_children && right_child_flag_set &&
          vieter_tree_node_validate(node->children[0], passed_black_nodes,
                                    expected_black_nodes) &&
          vieter_tree_node_validate(node->children[1], passed_black_nodes,
@@ -128,6 +132,14 @@ vieter_tree_node *vieter_tree_node_rotate(vieter_tree_node *old_root,
                                           bool dir) {
   vieter_tree_node *new_root = old_root->children[1 - dir];
 
+  if (old_root->parent != NULL) {
+    vieter_tree_node_set_child(
+        old_root->parent, new_root,
+        vieter_tree_node_get(old_root, vieter_tree_node_right));
+  } else {
+    new_root->parent = NULL;
+  }
+
   // Right rotation
   if (dir) {
     vieter_tree_node_set_child(old_root, new_root->children[1], false);

src/tree/vieter_tree_balancing.h

@@ -17,4 +17,5 @@ void vieter_tree_node_balance_after_insert(vieter_tree_node *node);
  */
 void vieter_tree_node_remove_balanced(vieter_tree_node *node);
 
+vieter_tree_node *vieter_tree_node_rotate(vieter_tree_node *old_root, bool dir);
 #endif

test/tree/test_balancing.c

@@ -0,0 +1,56 @@
+#include "acutest.h"
+#include "vieter_tree_internal.h"
+#include "vieter_tree_node.h"
+#include "vieter_tree_balancing.h"
+
+void test_rotate_right() {
+    vieter_tree_node *a = vieter_tree_node_init();
+    vieter_tree_node *b = vieter_tree_node_init();
+    vieter_tree_node *p = vieter_tree_node_init();
+
+    vieter_tree_node_set_child(p, a, false);
+    vieter_tree_node_set_child(p, b, true);
+
+    vieter_tree_node *c = vieter_tree_node_init();
+    vieter_tree_node *q = vieter_tree_node_init();
+
+    vieter_tree_node_set_child(q, p, false);
+    vieter_tree_node_set_child(q, c, true);
+
+    vieter_tree_node *new_root = vieter_tree_node_rotate(q, true);
+
+    TEST_CHECK(new_root == p);
+    TEST_CHECK(new_root->children[0] == a);
+    TEST_CHECK(new_root->children[1] == q);
+    TEST_CHECK(new_root->children[1]->children[0] == b);
+    TEST_CHECK(new_root->children[1]->children[1] == c);
+}
+
+void test_rotate_left() {
+    vieter_tree_node *b = vieter_tree_node_init();
+    vieter_tree_node *c = vieter_tree_node_init();
+    vieter_tree_node *q = vieter_tree_node_init();
+
+    vieter_tree_node_set_child(q, b, false);
+    vieter_tree_node_set_child(q, c, true);
+
+    vieter_tree_node *a = vieter_tree_node_init();
+    vieter_tree_node *p = vieter_tree_node_init();
+
+    vieter_tree_node_set_child(p, a, false);
+    vieter_tree_node_set_child(p, q, true);
+
+    vieter_tree_node *new_root = vieter_tree_node_rotate(p, false);
+
+    TEST_CHECK(new_root == q);
+    TEST_CHECK(new_root->children[0] == p);
+    TEST_CHECK(new_root->children[1] == c);
+    TEST_CHECK(new_root->children[0]->children[0] == a);
+    TEST_CHECK(new_root->children[0]->children[1] == b);
+}
+
+TEST_LIST = {
+    {"tree tree rotate right", test_rotate_right},
+    {"tree tree rotate left", test_rotate_left},
+    {NULL, NULL}
+};

test/tree/test_tree.c

@@ -42,7 +42,7 @@ void test_remove() {
 
     void *out;
 
-    for (uint64_t i = 0; i < 25; i++) {
+    for (uint64_t i = 0; i < 100; i++) {
         TEST_CHECK(vieter_tree_search(&out, tree, i) == vieter_tree_ok);
         TEST_CHECK(vieter_tree_remove(&out, tree, i) == vieter_tree_ok);
         TEST_CHECK(vieter_tree_validate(tree));