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fibonacciheap.py
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fibonacciheap.py
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class FibonacciNode:
degree = 0
p = None
child = None
mark = False
left = None
right = None
def __init__(self, k):
self.key = k
def __iter__(self):
"""
generate a list of children of the node for iteration
"""
self.children = []
self.index = 0
if self.child is not None:
child = self.child
while True:
self.children.append(child)
if child != self.child.left:
child = child.right
else:
break
return self
def next(self):
if self.index < len(self.children):
self.index = self.index + 1
return self.children[self.index - 1]
else:
raise StopIteration
def insert(self, x):
"""
insert x to the left of node
:param x:
:return:
"""
x.left = self.left
x.right = self
self.left.right = x
self.left = x
def concatenate(self, x):
"""
concatenate two lists represented by the node and x,
x mustn't be None
:param x:
:return:
"""
self.left.right = x.right
x.right.left = self.left
self.left = x
x.right = self
def remove(self):
self.left.right = self.right
self.right.left = self.left
def add_child(self, y):
self.degree = self.degree + 1
y.mark = False
y.p = self
if self.child is None:
self.child = y
y.left = y
y.right = y
else:
self.child.insert(y)
print("y.left.key = {}, y.right.key = {}".format(y.left.key, y.right.key))
def remove_child(self, y):
self.degree = self.degree - 1
if y.right == y:
self.child = None
elif y == self.child:
self.child = y.left
y.remove()
else:
y.remove()
class FibonacciHeap:
def __init__(self):
self.n = 0
self.minimum = None
def __iter__(self):
"""
generate a list of children of the node for iteration
:return:
"""
self.root_list = []
self.index = 0
if self.minimum is not None:
root = self.minimum
while True:
self.root_list.append(root)
if root != self.minimum.left:
root = root.right
else:
break
return self
def next(self):
if self.index < len(self.root_list):
self.index = self.index + 1
return self.root_list[self.index - 1]
else:
raise StopIteration
def __repr__(self):
s = ''
x = self.minimum
if x is not None:
while True:
s = s + '\t' + str(x.key)
if x == self.minimum.left:
break
else:
x = x.right
return s
else:
return ''
def insert(self, x):
"""
insert the node x into the root list of fibonacci heap
:param x:
:return:
"""
x.p = None
if self.minimum is None:
self.minimum = x
x.left = x
x.right = x
else:
self.minimum.insert(x)
if x.key < self.minimum.key:
self.minimum = x
self.n = self.n + 1
def minimum(self):
return self.minimum
def union(self, h):
cat = FibonacciHeap()
if self.minimum is None:
return h
elif h.minimum is None:
return self
else:
self.minimum.concatenate(h.minimum)
if self.minimum.key <= h.minimum.key:
cat.minimum = self.minimum
else:
cat.minimum = h.minimum
cat.n = self.n + h.n
return cat
def extract_min(self):
z = self.minimum
if z is not None:
for child in z:
self.insert(child)
z.remove()
if z == z.right:
self.minimum = None
else:
self.minimum = z.right
self.consolidate()
self.n = self.n - 1
return z
def consolidate(self):
D = self.n // 2
A = [None] * (D + 1)
left = self.minimum.left
w = self.minimum
for w in self:
x = w
d = x.degree
print('w.key = {}'.format(w.key))
print('w.degree = {}'.format(w.degree))
while A[d] is not None:
y = A[d]
if x.key > y.key:
x, y = y, x
self.link(y, x)
A[d] = None
d = d + 1
A[d] = x
self.minimum = None
for i in A:
if i is not None:
self.insert(i)
@staticmethod
def link(y, x):
y.remove()
x.add_child(y)
def decrease_key(self, x, k):
if k > x.key:
print("new key is greater than current key")
return
x.key = k
y = x.p
if y is not None and x.key < y.key:
self.cut(x, y)
self.cascading_cut(y)
if x.key < self.minimum.key:
self.minimum = x
def cut(self, x, y):
y.remove_child(x)
x.mark = False
self.insert(x)
def cascading_cut(self, y):
z = y.p
if z is not None:
if y.mark is False:
y.mark = True
else:
self.cut(y, z)
self.cascading_cut(z)
def delete(self, x):
self.decrease_key(x, float("-Inf"))
self.extract_min()