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| 1 // Copyright 2009 the V8 project authors. All rights reserved. |
| 2 // Redistribution and use in source and binary forms, with or without |
| 3 // modification, are permitted provided that the following conditions are |
| 4 // met: |
| 5 // |
| 6 // * Redistributions of source code must retain the above copyright |
| 7 // notice, this list of conditions and the following disclaimer. |
| 8 // * Redistributions in binary form must reproduce the above |
| 9 // copyright notice, this list of conditions and the following |
| 10 // disclaimer in the documentation and/or other materials provided |
| 11 // with the distribution. |
| 12 // * Neither the name of Google Inc. nor the names of its |
| 13 // contributors may be used to endorse or promote products derived |
| 14 // from this software without specific prior written permission. |
| 15 // |
| 16 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| 17 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| 18 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
| 19 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
| 20 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| 21 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
| 22 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| 23 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| 24 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| 25 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
| 26 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| 27 |
| 28 |
| 29 // A namespace stub. It will become more clear how to declare it properly |
| 30 // during integration of this script into Dev Tools. |
| 31 goog = { structs: {} }; |
| 32 |
| 33 |
| 34 /** |
| 35 * Constructs a Splay tree. A splay tree is a self-balancing binary |
| 36 * search tree with the additional property that recently accessed |
| 37 * elements are quick to access again. It performs basic operations |
| 38 * such as insertion, look-up and removal in O(log(n)) amortized time. |
| 39 * |
| 40 * @constructor |
| 41 */ |
| 42 goog.structs.SplayTree = function() { |
| 43 }; |
| 44 |
| 45 |
| 46 /** |
| 47 * Pointer to the root node of the tree. |
| 48 * |
| 49 * @type {goog.structs.SplayTree.Node} |
| 50 * @private |
| 51 */ |
| 52 goog.structs.SplayTree.prototype.root_ = null; |
| 53 |
| 54 |
| 55 /** |
| 56 * @return {boolean} Whether the tree is empty. |
| 57 */ |
| 58 goog.structs.SplayTree.prototype.isEmpty = function() { |
| 59 return !this.root_; |
| 60 }; |
| 61 |
| 62 |
| 63 |
| 64 /** |
| 65 * Inserts a node into the tree with the specified key and value if |
| 66 * the tree does not already contain a node with the specified key. If |
| 67 * the value is inserted, it becomes the root of the tree. |
| 68 * |
| 69 * @param {number} key Key to insert into the tree. |
| 70 * @param {*} value Value to insert into the tree. |
| 71 */ |
| 72 goog.structs.SplayTree.prototype.insert = function(key, value) { |
| 73 if (this.isEmpty()) { |
| 74 this.root_ = new goog.structs.SplayTree.Node(key, value); |
| 75 return; |
| 76 } |
| 77 // Splay on the key to move the last node on the search path for |
| 78 // the key to the root of the tree. |
| 79 this.splay_(key); |
| 80 if (this.root_.key == key) { |
| 81 return; |
| 82 } |
| 83 var node = new goog.structs.SplayTree.Node(key, value); |
| 84 if (key > this.root_.key) { |
| 85 node.left = this.root_; |
| 86 node.right = this.root_.right; |
| 87 this.root_.right = null; |
| 88 } else { |
| 89 node.right = this.root_; |
| 90 node.left = this.root_.left; |
| 91 this.root_.left = null; |
| 92 } |
| 93 this.root_ = node; |
| 94 }; |
| 95 |
| 96 |
| 97 |
| 98 /** |
| 99 * Removes a node with the specified key from the tree if the tree |
| 100 * contains a node with this key. The removed node is returned. If the |
| 101 * key is not found, an exception is thrown. |
| 102 * |
| 103 * @param {number} key Key to find and remove from the tree. |
| 104 * @return {goog.structs.SplayTree.Node} The removed node. |
| 105 */ |
| 106 goog.structs.SplayTree.prototype.remove = function(key) { |
| 107 if (this.isEmpty()) { |
| 108 throw Error('Key not found: ' + key); |
| 109 } |
| 110 this.splay_(key); |
| 111 if (this.root_.key != key) { |
| 112 throw Error('Key not found: ' + key); |
| 113 } |
| 114 var removed = this.root_; |
| 115 if (!this.root_.left) { |
| 116 this.root_ = this.root_.right; |
| 117 } else { |
| 118 var right = this.root_.right; |
| 119 this.root_ = this.root_.left; |
| 120 // Splay to make sure that the new root has an empty right child. |
| 121 this.splay_(key); |
| 122 // Insert the original right child as the right child of the new |
| 123 // root. |
| 124 this.root_.right = right; |
| 125 } |
| 126 return removed; |
| 127 }; |
| 128 |
| 129 |
| 130 /** |
| 131 * Returns the node having the specified key or null if the tree doesn't contain |
| 132 * a node with the specified key. |
| 133 * |
| 134 * @param {number} key Key to find in the tree. |
| 135 * @return {goog.structs.SplayTree.Node} Node having the specified key. |
| 136 */ |
| 137 goog.structs.SplayTree.prototype.find = function(key) { |
| 138 if (this.isEmpty()) { |
| 139 return null; |
| 140 } |
| 141 this.splay_(key); |
| 142 return this.root_.key == key ? this.root_ : null; |
| 143 }; |
| 144 |
| 145 |
| 146 /** |
| 147 * @return {goog.structs.SplayTree.Node} Node having the minimum key value. |
| 148 */ |
| 149 goog.structs.SplayTree.prototype.findMin = function() { |
| 150 if (this.isEmpty()) { |
| 151 return null; |
| 152 } |
| 153 var current = this.root_; |
| 154 while (current.left) { |
| 155 current = current.left; |
| 156 } |
| 157 return current; |
| 158 }; |
| 159 |
| 160 |
| 161 /** |
| 162 * @return {goog.structs.SplayTree.Node} Node having the maximum key value. |
| 163 */ |
| 164 goog.structs.SplayTree.prototype.findMax = function(opt_startNode) { |
| 165 if (this.isEmpty()) { |
| 166 return null; |
| 167 } |
| 168 var current = opt_startNode || this.root_; |
| 169 while (current.right) { |
| 170 current = current.right; |
| 171 } |
| 172 return current; |
| 173 }; |
| 174 |
| 175 |
| 176 /** |
| 177 * @return {goog.structs.SplayTree.Node} Node having the maximum key value that |
| 178 * is less or equal to the specified key value. |
| 179 */ |
| 180 goog.structs.SplayTree.prototype.findGreatestLessThan = function(key) { |
| 181 if (this.isEmpty()) { |
| 182 return null; |
| 183 } |
| 184 // Splay on the key to move the node with the given key or the last |
| 185 // node on the search path to the top of the tree. |
| 186 this.splay_(key); |
| 187 // Now the result is either the root node or the greatest node in |
| 188 // the left subtree. |
| 189 if (this.root_.key <= key) { |
| 190 return this.root_; |
| 191 } else if (this.root_.left) { |
| 192 return this.findMax(this.root_.left); |
| 193 } else { |
| 194 return null; |
| 195 } |
| 196 }; |
| 197 |
| 198 |
| 199 /** |
| 200 * @return {Array<*>} An array containing all the values of tree's nodes. |
| 201 */ |
| 202 goog.structs.SplayTree.prototype.exportValues = function() { |
| 203 var result = []; |
| 204 this.traverse_(function(node) { result.push(node.value); }); |
| 205 return result; |
| 206 }; |
| 207 |
| 208 |
| 209 /** |
| 210 * Perform the splay operation for the given key. Moves the node with |
| 211 * the given key to the top of the tree. If no node has the given |
| 212 * key, the last node on the search path is moved to the top of the |
| 213 * tree. This is the simplified top-down splaying algorithm from: |
| 214 * "Self-adjusting Binary Search Trees" by Sleator and Tarjan |
| 215 * |
| 216 * @param {number} key Key to splay the tree on. |
| 217 * @private |
| 218 */ |
| 219 goog.structs.SplayTree.prototype.splay_ = function(key) { |
| 220 if (this.isEmpty()) { |
| 221 return; |
| 222 } |
| 223 // Create a dummy node. The use of the dummy node is a bit |
| 224 // counter-intuitive: The right child of the dummy node will hold |
| 225 // the L tree of the algorithm. The left child of the dummy node |
| 226 // will hold the R tree of the algorithm. Using a dummy node, left |
| 227 // and right will always be nodes and we avoid special cases. |
| 228 var dummy, left, right; |
| 229 dummy = left = right = new goog.structs.SplayTree.Node(null, null); |
| 230 var current = this.root_; |
| 231 while (true) { |
| 232 if (key < current.key) { |
| 233 if (!current.left) { |
| 234 break; |
| 235 } |
| 236 if (key < current.left.key) { |
| 237 // Rotate right. |
| 238 var tmp = current.left; |
| 239 current.left = tmp.right; |
| 240 tmp.right = current; |
| 241 current = tmp; |
| 242 if (!current.left) { |
| 243 break; |
| 244 } |
| 245 } |
| 246 // Link right. |
| 247 right.left = current; |
| 248 right = current; |
| 249 current = current.left; |
| 250 } else if (key > current.key) { |
| 251 if (!current.right) { |
| 252 break; |
| 253 } |
| 254 if (key > current.right.key) { |
| 255 // Rotate left. |
| 256 var tmp = current.right; |
| 257 current.right = tmp.left; |
| 258 tmp.left = current; |
| 259 current = tmp; |
| 260 if (!current.right) { |
| 261 break; |
| 262 } |
| 263 } |
| 264 // Link left. |
| 265 left.right = current; |
| 266 left = current; |
| 267 current = current.right; |
| 268 } else { |
| 269 break; |
| 270 } |
| 271 } |
| 272 // Assemble. |
| 273 left.right = current.left; |
| 274 right.left = current.right; |
| 275 current.left = dummy.right; |
| 276 current.right = dummy.left; |
| 277 this.root_ = current; |
| 278 }; |
| 279 |
| 280 |
| 281 /** |
| 282 * Performs a preorder traversal of the tree. |
| 283 * |
| 284 * @param {function(goog.structs.SplayTree.Node)} f Visitor function. |
| 285 * @private |
| 286 */ |
| 287 goog.structs.SplayTree.prototype.traverse_ = function(f) { |
| 288 var nodesToVisit = [this.root_]; |
| 289 while (nodesToVisit.length > 0) { |
| 290 var node = nodesToVisit.shift(); |
| 291 if (node == null) { |
| 292 continue; |
| 293 } |
| 294 f(node); |
| 295 nodesToVisit.push(node.left); |
| 296 nodesToVisit.push(node.right); |
| 297 } |
| 298 }; |
| 299 |
| 300 |
| 301 /** |
| 302 * Constructs a Splay tree node. |
| 303 * |
| 304 * @param {number} key Key. |
| 305 * @param {*} value Value. |
| 306 */ |
| 307 goog.structs.SplayTree.Node = function(key, value) { |
| 308 this.key = key; |
| 309 this.value = value; |
| 310 }; |
| 311 |
| 312 |
| 313 /** |
| 314 * @type {goog.structs.SplayTree.Node} |
| 315 */ |
| 316 goog.structs.SplayTree.Node.prototype.left = null; |
| 317 |
| 318 |
| 319 /** |
| 320 * @type {goog.structs.SplayTree.Node} |
| 321 */ |
| 322 goog.structs.SplayTree.Node.prototype.right = null; |
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