Created
July 21, 2013 03:51
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AVL tree in python, no deletions
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#!/usr/local/bin/python3 | |
class AVLTree: | |
def __init__(self, data): | |
self.data = data | |
self.lhs = None | |
self.rhs = None | |
def insert(self, data): | |
if data == self.data: | |
return | |
self._insert(data, 'lhs' if data < self.data else 'rhs') | |
self._rebalance() | |
def _insert(self, data, side): | |
child = getattr(self, side) | |
if child: | |
child.insert(data) | |
else: | |
setattr(self, side, AVLTree(data)) | |
def _rebalance(self): | |
balance = self._height(self.lhs) - self._height(self.rhs) | |
if balance > 1: | |
llheight = self._height(self.lhs.lhs) | |
lrheight = self._height(self.lhs.rhs) | |
if lrheight > llheight: | |
self.lhs._rotate_left() | |
self._rotate_right() | |
elif balance < -1: | |
rlheight = self._height(self.rhs.lhs) | |
rrheight = self._height(self.rhs.rhs) | |
if rlheight > rrheight: | |
self.rhs._rotate_right() | |
self._rotate_left() | |
def _height(self, node): | |
if not node: | |
return 0 | |
else: | |
return 1 + max(self._height(node.lhs), self._height(node.rhs)) | |
def _rotate_left(self): | |
cog, A, B, C = self.rhs, self.lhs, self.rhs.lhs, self.rhs.rhs | |
self.lhs, self.data, cog.data = cog, cog.data, self.data | |
self.rhs, cog.lhs, cog.rhs = C, A, B | |
def _rotate_right(self): | |
cog, B, C, D = self.lhs, self.lhs.lhs, self.lhs.rhs, self.rhs | |
self.rhs, self.data, cog.data = cog, cog.data, self.data | |
self.lhs, cog.lhs, cog.rhs = B, C, D | |
def rigid(self): | |
ok = abs(self._height(self.lhs) - self._height(self.rhs)) <= 1 | |
return ok and \ | |
self.lhs.rigid() if self.lhs else True and \ | |
self.rhs.rigid() if self.rhs else True | |
def show(self, indent = 0): | |
if self.lhs: | |
self.lhs.show(indent + 1) | |
print(' ' * (2 * indent) + '> ' + str(self.data)) | |
if self.rhs: | |
self.rhs.show(indent + 1) | |
if __name__ == '__main__': | |
import random | |
t = AVLTree(0) | |
for x in range(100): | |
t.insert(random.random()) | |
assert t.rigid() | |
t.show() | |
dt = AVLTree(0) | |
for x in range(100): | |
t.insert(x) | |
assert t.rigid() | |
t.show() |
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