Reimplement Splay Tree in JavaScript (and add unit tests!).

test/mjsunit/tools/splaytree.js

+// Copyright 2009 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * 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.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// 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
+// OWNER 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.
+
+// Load the Splay tree implementation from <project root>/tools.
+// Files: tools/splaytree.js
+
+
+(function testIsEmpty() {
+  var tree = new goog.structs.SplayTree();
+  assertTrue(tree.isEmpty());
+  tree.insert(0, 'value');
+  assertFalse(tree.isEmpty());
+})();
+
+
+(function testExportValues() {
+  var tree = new goog.structs.SplayTree();
+  assertArrayEquals([], tree.exportValues());
+  tree.insert(0, 'value');
+  assertArrayEquals(['value'], tree.exportValues());
+  tree.insert(0, 'value');
+  assertArrayEquals(['value'], tree.exportValues());
+})();
+
+
+function createSampleTree() {
+  // Creates the following tree:
+  //           50
+  //          /  \
+  //         30  60
+  //        /  \   \
+  //       10  40  90
+  //         \    /  \
+  //         20  70 100
+  //        /      \
+  //       15      80
+  //
+  // We can't use the 'insert' method because it also uses 'splay_'.
+  return { key: 50, value: 50,
+      left: { key: 30, value: 30,
+              left: { key: 10, value: 10, left: null,
+                      right: { key: 20, value: 20,
+                               left: { key: 15, value: 15,
+                                       left: null, right: null },
+                               right: null } },
+              right: { key: 40, value: 40, left: null, right: null } },
+      right: { key: 60, value: 60, left: null,
+               right: { key: 90, value: 90,
+                        left: { key: 70, value: 70, left: null,
+                                right: { key: 80, value: 80,
+                                         left: null, right: null } },
+                        right: { key: 100, value: 100,
+                                 left: null, right: null } } } };
+};
+
+
+(function testSplay() {
+  var tree = new goog.structs.SplayTree();
+  tree.root_ = createSampleTree();
+  assertArrayEquals(['50', '30', '60', '10', '40', '90', '20', '70', '100', '15', '80'],
+                    tree.exportValues());
+  tree.splay_(50);
+  assertArrayEquals(['50', '30', '60', '10', '40', '90', '20', '70', '100', '15', '80'],
+                    tree.exportValues());
+  tree.splay_(80);
+  assertArrayEquals(['80', '60', '90', '50', '70', '100', '30', '10', '40', '20', '15'],
+                    tree.exportValues());
+})();
+
+
+(function testInsert() {
+  var tree = new goog.structs.SplayTree();
+  tree.insert(5, 'root');
+  tree.insert(3, 'left');
+  assertArrayEquals(['left', 'root'], tree.exportValues());
+  tree.insert(7, 'right');
+  assertArrayEquals(['right', 'root', 'left'], tree.exportValues());
+})();
+
+
+(function testFind() {
+  var tree = new goog.structs.SplayTree();
+  tree.insert(5, 'root');
+  tree.insert(3, 'left');
+  tree.insert(7, 'right');
+  assertEquals('root', tree.find(5).value);
+  assertEquals('left', tree.find(3).value);
+  assertEquals('right', tree.find(7).value);
+  assertEquals(null, tree.find(0));
+  assertEquals(null, tree.find(100));
+  assertEquals(null, tree.find(-100));
+})();
+
+
+(function testFindMin() {
+  var tree = new goog.structs.SplayTree();
+  assertEquals(null, tree.findMin());
+  tree.insert(5, 'root');
+  tree.insert(3, 'left');
+  tree.insert(7, 'right');
+  assertEquals('left', tree.findMin().value);
+})();
+
+
+(function testFindMax() {
+  var tree = new goog.structs.SplayTree();
+  assertEquals(null, tree.findMax());
+  tree.insert(5, 'root');
+  tree.insert(3, 'left');
+  tree.insert(7, 'right');
+  assertEquals('right', tree.findMax().value);
+})();
+
+
+(function testFindGreatestLessThan() {
+  var tree = new goog.structs.SplayTree();
+  assertEquals(null, tree.findGreatestLessThan(10));
+  tree.insert(5, 'root');
+  tree.insert(3, 'left');
+  tree.insert(7, 'right');
+  assertEquals('right', tree.findGreatestLessThan(10).value);
+  assertEquals('right', tree.findGreatestLessThan(7).value);
+  assertEquals('root', tree.findGreatestLessThan(6).value);
+  assertEquals('left', tree.findGreatestLessThan(4).value);
+  assertEquals(null, tree.findGreatestLessThan(2));
+})();
+
+
+(function testRemove() {
+  var tree = new goog.structs.SplayTree();
+  assertThrows('tree.remove(5)');
+  tree.insert(5, 'root');
+  tree.insert(3, 'left');
+  tree.insert(7, 'right');
+  assertThrows('tree.remove(1)');
+  assertThrows('tree.remove(6)');
+  assertThrows('tree.remove(10)');
+  assertEquals('root', tree.remove(5).value);
+  assertEquals('left', tree.remove(3).value);
+  assertEquals('right', tree.remove(7).value);
+  assertArrayEquals([], tree.exportValues());
+})();