feat(tree): initially working binary tree

Makefile

@@ -43,7 +43,7 @@ objs: $(OBJS)
 
 .PHONY: vieter
 vieter: $(LIB)
-$(BUILD_DIR)/$(LIB_FILENAME): $(OBJS)
+$(LIB): $(OBJS)
 	ar -rcs $@ $(OBJS)
 
 $(BUILD_DIR)/$(SRC_DIR)/%.c.o: $(SRC_DIR)/%.c

src/tree/node.c

@@ -4,9 +4,35 @@ vieter_tree_node *vieter_tree_node_init() {
   return calloc(1, sizeof(vieter_tree_node));
 }
 
-vieter_tree_error vieter_tree_node_insert(vieter_tree_node *node, uint64_t key,
+void vieter_tree_node_add_child(vieter_tree_node *parent, uint64_t key,
+                                vieter_tree_node *child) {
+  if (parent == NULL) {
+    return;
+  }
+
+  if (key < parent->key) {
+    parent->left = child;
+  } else {
+    parent->right = child;
+  }
+
+  if (child != NULL) {
+    child->parent = parent;
+  }
+}
+
+void vieter_tree_node_replace(vieter_tree_node *to_replace,
+                              vieter_tree_node *replacement) {
+  to_replace->key = replacement->key;
+  to_replace->data = replacement->data;
+  to_replace->left = replacement->left;
+  to_replace->right = replacement->right;
+}
+
+vieter_tree_error vieter_tree_node_insert(vieter_tree_node *root, uint64_t key,
                                           void *data) {
-  vieter_tree_node *parent = node;
+  vieter_tree_node *node = root;
+  vieter_tree_node *parent = root;
 
   while (node != NULL) {
     if (node->key == key) {
@@ -15,7 +41,7 @@ vieter_tree_error vieter_tree_node_insert(vieter_tree_node *node, uint64_t key,
 
     parent = node;
 
-    if (key < node->key) {
+    if (key < parent->key) {
       node = parent->left;
     } else {
       node = parent->right;
@@ -25,22 +51,20 @@ vieter_tree_error vieter_tree_node_insert(vieter_tree_node *node, uint64_t key,
   vieter_tree_node *new_node = vieter_tree_node_init();
   new_node->key = key;
   new_node->data = data;
-  new_node->parent = parent;
 
-  if (key < node->key) {
-    parent->left = new_node;
-  } else {
-    parent->right = new_node;
-  }
+  vieter_tree_node_add_child(parent, key, new_node);
 
   return vieter_tree_ok;
 }
 
-vieter_tree_error vieter_tree_node_search(void **out, vieter_tree_node *node,
-                                          uint64_t key) {
+vieter_tree_error vieter_tree_node_search_node(vieter_tree_node **out,
+                                               vieter_tree_node *root,
+                                               uint64_t key) {
+  vieter_tree_node *node = root;
+
   while (node != NULL) {
     if (node->key == key) {
-      *out = node->data;
+      *out = node;
 
       return vieter_tree_ok;
     }
@@ -55,7 +79,80 @@ vieter_tree_error vieter_tree_node_search(void **out, vieter_tree_node *node,
   return vieter_tree_not_present;
 }
 
-vieter_tree_error vieter_tree_node_remove(void **out, vieter_tree_node *node,
+vieter_tree_error vieter_tree_node_search(void **out, vieter_tree_node *root,
                                           uint64_t key) {
-  return vieter_tree_not_present;
+  vieter_tree_node *target;
+  vieter_tree_error res = vieter_tree_node_search_node(&target, root, key);
+
+  if (res != vieter_tree_ok) {
+    return res;
+  }
+
+  *out = target->data;
+
+  return vieter_tree_ok;
+}
+
+vieter_tree_node *vieter_tree_node_successor(vieter_tree_node *node) {
+  if ((node->left != NULL) ^ (node->right != NULL)) {
+    return node->left != NULL ? node->left : node->right;
+  }
+
+  node = node->right;
+
+  while (node->left != NULL) {
+    node = node->left;
+  }
+
+  return node;
+}
+
+vieter_tree_error vieter_tree_node_remove(void **out, vieter_tree_node *root,
+                                          uint64_t key) {
+  vieter_tree_node *target;
+  vieter_tree_error res = vieter_tree_node_search_node(&target, root, key);
+
+  if (res != vieter_tree_ok) {
+    return res;
+  }
+
+  *out = target->data;
+
+  if (target->left == NULL && target->right == NULL) {
+    vieter_tree_node_add_child(target->parent, target->key, NULL);
+
+    free(target);
+  } else if ((target->left == NULL) ^ (target->right == NULL)) {
+    vieter_tree_node *child =
+        target->left != NULL ? target->left : target->right;
+
+    if (target->parent != NULL) {
+      vieter_tree_node_add_child(target->parent, child->key, child);
+      free(target);
+    } else {
+      vieter_tree_node_replace(target, child);
+      free(child);
+    }
+
+  } else {
+    vieter_tree_node *replacement = target->right;
+
+    while (replacement->left != NULL) {
+      replacement = replacement->left;
+    }
+
+    // We use replacement->key here because the right child can be NULL, so
+    // reading its key isn't safe. Using replacement->key however, the child
+    // will still get placed into the right location because of how binary
+    // trees work.
+    vieter_tree_node_add_child(replacement->parent, replacement->key,
+                               replacement->right);
+
+    target->key = replacement->key;
+    target->data = replacement->data;
+
+    free(replacement);
+  }
+
+  return vieter_tree_ok;
 }

src/tree/node.h

@@ -14,10 +14,15 @@ typedef struct vieter_tree_node {
 
 vieter_tree_node *vieter_tree_node_init();
 
-vieter_tree_error vieter_tree_node_insert(vieter_tree_node *node, uint64_t key, void *data);
+vieter_tree_error vieter_tree_node_insert(vieter_tree_node *root, uint64_t key, void *data);
 
-vieter_tree_error vieter_tree_node_search(void **out, vieter_tree_node *node, uint64_t key);
+vieter_tree_error vieter_tree_node_search_node(vieter_tree_node **out, vieter_tree_node *root, uint64_t key);
+vieter_tree_error vieter_tree_node_search(void **out, vieter_tree_node *root, uint64_t key);
 
-vieter_tree_error vieter_tree_node_remove(void **out, vieter_tree_node *node, uint64_t key);
+vieter_tree_error vieter_tree_node_remove(void **out, vieter_tree_node *root, uint64_t key);
+
+vieter_tree_node *vieter_tree_node_successor(vieter_tree_node *node);
+
+void vieter_tree_node_replace(vieter_tree_node *to_replace, vieter_tree_node *replacement);
 
 #endif

test/tree/test_binary_tree.c

@@ -17,16 +17,37 @@ void test_insert() {
 
     for (uint64_t i = 0; i < 25; i++) {
         TEST_CHECK(vieter_tree_insert(tree, i, NULL) == vieter_tree_ok);
+        TEST_SIZE(tree, i + 1);
     }
 
     void *out;
 
     for (uint64_t i = 0; i < 25; i++) {
+        TEST_CHECK(vieter_tree_search(&out, tree, i) == vieter_tree_ok);
         TEST_CHECK(vieter_tree_insert(tree, i, NULL) == vieter_tree_already_present);
         TEST_CHECK(vieter_tree_search(&out, tree, i) == vieter_tree_ok);
     }
 }
 
+void test_remove() {
+    vieter_tree *tree = vieter_tree_init();
+
+    for (uint64_t i = 0; i < 25; i++) {
+        TEST_CHECK(vieter_tree_insert(tree, i, NULL) == vieter_tree_ok);
+    }
+
+    void *out;
+
+    for (uint64_t i = 0; i < 25; 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_search(&out, tree, i) == vieter_tree_not_present);
+    }
+}
+
 TEST_LIST = {
+    {"test_init", test_init},
+    {"test_insert", test_insert},
+    {"test_remove", test_remove},
     {NULL, NULL}
 };