From: a bellenir <a@bellenir.com>
Date: Wed, 6 Aug 2014 22:20:20 +0000 (+0000)
Subject: remove root in otherwise empty tree
X-Git-Url: https://git.mdlowis.com/?a=commitdiff_plain;h=921f1c60f8280ef5fb4f3a8190342adb94070840;p=projs%2Flibcds.git

remove root in otherwise empty tree
---

diff --git a/source/rb/rb.c b/source/rb/rb.c
index 990715e..a2e9728 100644
--- a/source/rb/rb.c
+++ b/source/rb/rb.c
@@ -174,8 +174,10 @@ static void rb_tree_delete_node(rb_tree_t* tree, rb_node_t* node){
 	if(node->left && node->right){
 		//has two children. TODO
 	}else{
+		//node has at most one non-leaf child
 		rb_node_t* parent = node->parent;
 		if(RED == node_color(node)){
+			//node is red and has only leaf children or tree is invalid.
 			if(node == parent->left) parent->left = NULL;
 			else parent->right = NULL;
 			node->parent = NULL;
@@ -203,6 +205,14 @@ static void rb_tree_delete_node(rb_tree_t* tree, rb_node_t* node){
 			node->right = NULL;
 			node->parent = NULL;
 			mem_release(node);
+		} else if(node == tree->root){
+			//at most one child. no red children :: no children.
+			tree->root = NULL;
+			//pointers should already be null.
+			mem_release(node);
+		} else {
+			//node is not root.
+			//node is black, and has only leaf children or tree is invalid.
 		}
 	}
 }
diff --git a/tests/test_rb.c b/tests/test_rb.c
index ea6d9f0..7a97f73 100644
--- a/tests/test_rb.c
+++ b/tests/test_rb.c
@@ -458,5 +458,19 @@ TEST_SUITE(RB) {
 		mem_release(node1);
 		mem_release(tree);
 	}
+	TEST(Verify_rb_delete_root_node_with_no_children){
+		rb_tree_t* tree = rb_tree_new();
+		rb_node_t* node1 = rb_tree_insert(tree, 88);
+		mem_retain(node1);
+		rb_tree_delete(tree, 88);
+		CHECK(1 == mem_num_references(node1));
+		CHECK(NULL == tree->root);
+		CHECK(NULL == node1->left);
+		CHECK(NULL == node1->right);
+		CHECK(NULL == node1->parent);
+		CHECK(rb_tree_is_valid(tree));
+		mem_release(node1);
+		mem_release(tree);
+	}
 }