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diff --git a/tools/splaytree.py b/tools/splaytree.py
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-# Copyright 2008 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.
-
-
-class Node(object):
- """Nodes in the splay tree."""
-
- def __init__(self, key, value):
- self.key = key
- self.value = value
- self.left = None
- self.right = None
-
-
-class KeyNotFoundError(Exception):
- """KeyNotFoundError is raised when removing a non-existing node."""
-
- def __init__(self, key):
- self.key = key
-
-
-class SplayTree(object):
- """The splay tree itself is just a reference to the root of the tree."""
-
- def __init__(self):
- """Create a new SplayTree."""
- self.root = None
-
- def IsEmpty(self):
- """Is the SplayTree empty?"""
- return not self.root
-
- def Insert(self, key, value):
- """Insert a new node in the SplayTree."""
- # If the tree is empty, insert the new node.
- if self.IsEmpty():
- self.root = Node(key, value)
- return
- # Splay on the key to move the last node on the search path for
- # the key to the root of the tree.
- self.Splay(key)
- # Ignore repeated insertions with the same key.
- if self.root.key == key:
- return
- # Insert the new node.
- node = Node(key, value)
- if key > self.root.key:
- node.left = self.root
- node.right = self.root.right
- self.root.right = None
- else:
- node.right = self.root
- node.left = self.root.left
- self.root.left = None
- self.root = node
-
- def Remove(self, key):
- """Remove the node with the given key from the SplayTree."""
- # Raise exception for key that is not found if the tree is empty.
- if self.IsEmpty():
- raise KeyNotFoundError(key)
- # Splay on the key to move the node with the given key to the top.
- self.Splay(key)
- # Raise exception for key that is not found.
- if self.root.key != key:
- raise KeyNotFoundError(key)
- removed = self.root
- # Link out the root node.
- if not self.root.left:
- # No left child, so the new tree is just the right child.
- self.root = self.root.right
- else:
- # Left child exists.
- right = self.root.right
- # Make the original left child the new root.
- self.root = self.root.left
- # Splay to make sure that the new root has an empty right child.
- self.Splay(key)
- # Insert the original right child as the right child of the new
- # root.
- self.root.right = right
- return removed
-
- def Find(self, key):
- """Returns the node with the given key or None if no such node exists."""
- if self.IsEmpty():
- return None
- self.Splay(key)
- if self.root.key == key:
- return self.root
- return None
-
- def FindMax(self):
- """Returns the node with the largest key value."""
- if self.IsEmpty():
- return None
- current = self.root
- while current.right != None:
- current = current.right
- return current
-
- # Returns the node with the smallest key value.
- def FindMin(self):
- if self.IsEmpty():
- return None
- current = self.root
- while current.left != None:
- current = current.left
- return current
-
- def FindGreatestsLessThan(self, key):
- """Returns node with greatest key less than or equal to the given key."""
- if self.IsEmpty():
- return None
- # Splay on the key to move the node with the given key or the last
- # node on the search path to the top of the tree.
- self.Splay(key)
- # Now the result is either the root node or the greatest node in
- # the left subtree.
- if self.root.key <= key:
- return self.root
- else:
- tmp = self.root
- self.root = self.root.left
- result = self.FindMax()
- self.root = tmp
- return result
-
- def ExportValueList(self):
- """Returns a list containing all the values of the nodes in the tree."""
- result = []
- nodes_to_visit = [self.root]
- while len(nodes_to_visit) > 0:
- node = nodes_to_visit.pop()
- if not node:
- continue
- result.append(node.value)
- nodes_to_visit.append(node.left)
- nodes_to_visit.append(node.right)
- return result
-
- def Splay(self, key):
- """Perform splay operation.
-
- Perform the splay operation for the given key. Moves the node with
- the given key to the top of the tree. If no node has the given
- key, the last node on the search path is moved to the top of the
- tree.
-
- This uses the simplified top-down splaying algorithm from:
-
- "Self-adjusting Binary Search Trees" by Sleator and Tarjan
-
- """
- if self.IsEmpty():
- return
- # Create a dummy node. The use of the dummy node is a bit
- # counter-intuitive: The right child of the dummy node will hold
- # the L tree of the algorithm. The left child of the dummy node
- # will hold the R tree of the algorithm. Using a dummy node, left
- # and right will always be nodes and we avoid special cases.
- dummy = left = right = Node(None, None)
- current = self.root
- while True:
- if key < current.key:
- if not current.left:
- break
- if key < current.left.key:
- # Rotate right.
- tmp = current.left
- current.left = tmp.right
- tmp.right = current
- current = tmp
- if not current.left:
- break
- # Link right.
- right.left = current
- right = current
- current = current.left
- elif key > current.key:
- if not current.right:
- break
- if key > current.right.key:
- # Rotate left.
- tmp = current.right
- current.right = tmp.left
- tmp.left = current
- current = tmp
- if not current.right:
- break
- # Link left.
- left.right = current
- left = current
- current = current.right
- else:
- break
- # Assemble.
- left.right = current.left
- right.left = current.right
- current.left = dummy.right
- current.right = dummy.left
- self.root = current