AK: Implement RedBlackTree container

This container is based on a balanced binary search tree, and as such
allows for O(logn) worst-case insertion, removal, and search, as well
as O(n) sorted iteration.

2 files changed, 111 insertions, 0 deletions

diff --git a/AK/Tests/CMakeLists.txt b/AK/Tests/CMakeLists.txt
index dc059a66fe..b12c459907 100644
--- a/AK/Tests/CMakeLists.txt
+++ b/AK/Tests/CMakeLists.txt
@@ -39,6 +39,7 @@ set(AK_TEST_SOURCES
     TestOptional.cpp
     TestQueue.cpp
     TestQuickSort.cpp
+    TestRedBlackTree.cpp
     TestRefPtr.cpp
     TestSinglyLinkedList.cpp
     TestSourceGenerator.cpp
diff --git a/AK/Tests/TestRedBlackTree.cpp b/AK/Tests/TestRedBlackTree.cpp
new file mode 100644
index 0000000000..d7115dc217
--- /dev/null
+++ b/AK/Tests/TestRedBlackTree.cpp
@@ -0,0 +1,110 @@
+/*
+ * Copyright (c) 2021, Idan Horowitz <idan.horowitz@gmail.com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <AK/TestSuite.h>
+
+#include <AK/Random.h>
+#include <AK/RedBlackTree.h>
+
+TEST_CASE(construct)
+{
+    RedBlackTree<int, int> empty;
+    EXPECT(empty.is_empty());
+    EXPECT(empty.size() == 0);
+}
+
+TEST_CASE(ints)
+{
+    RedBlackTree<int, int> ints;
+    ints.insert(1, 10);
+    ints.insert(3, 20);
+    ints.insert(2, 30);
+    EXPECT_EQ(ints.size(), 3u);
+    EXPECT_EQ(*ints.find(3), 20);
+    EXPECT_EQ(*ints.find(2), 30);
+    EXPECT_EQ(*ints.find(1), 10);
+    EXPECT(!ints.remove(4));
+    EXPECT(ints.remove(2));
+    EXPECT(ints.remove(1));
+    EXPECT(ints.remove(3));
+    EXPECT_EQ(ints.size(), 0u);
+}
+
+TEST_CASE(largest_smaller_than)
+{
+    RedBlackTree<int, int> ints;
+    ints.insert(1, 10);
+    ints.insert(11, 20);
+    ints.insert(21, 30);
+    EXPECT_EQ(ints.size(), 3u);
+    EXPECT_EQ(*ints.find_largest_not_above(3), 10);
+    EXPECT_EQ(*ints.find_largest_not_above(17), 20);
+    EXPECT_EQ(*ints.find_largest_not_above(22), 30);
+    EXPECT_EQ(ints.find_largest_not_above(-5), nullptr);
+}
+
+TEST_CASE(key_ordered_iteration)
+{
+    constexpr auto amount = 10000;
+    RedBlackTree<int, size_t> test;
+    Array<int, amount> keys {};
+
+    // generate random key order
+    for (int i = 0; i < amount; i++) {
+        keys[i] = i;
+    }
+    for (size_t i = 0; i < amount; i++) {
+        swap(keys[i], keys[get_random<size_t>() % amount]);
+    }
+
+    // insert random keys
+    for (size_t i = 0; i < amount; i++) {
+        test.insert(keys[i], keys[i]);
+    }
+
+    // check key-ordered iteration
+    size_t index = 0;
+    for (auto& value : test) {
+        EXPECT(value == index++);
+    }
+
+    // ensure we can remove all of them (aka, tree structure is not destroyed somehow)
+    for (size_t i = 0; i < amount; i++) {
+        EXPECT(test.remove(i));
+    }
+}
+
+TEST_CASE(clear)
+{
+    RedBlackTree<size_t, size_t> test;
+    for (size_t i = 0; i < 1000; i++) {
+        test.insert(i, i);
+    }
+    test.clear();
+    EXPECT_EQ(test.size(), 0u);
+}
+
+TEST_MAIN(RedBlackTree)