def heapsort(array):
"""Implements heapsort in-place using heap.Heap. Insert all
the values in (via heapify in O(n) ) and the read them
out in max order, inserting into the correct place in the
orig list.
This uses an additional O(n) space since we create another copy in the
Heap. We could do this in place if the heap tracked the max heap size
separate from the max array size
"""
heapy = Heap(array)
for i in reversed(range(len(array))):
array[i] = heapy.extract_max()
def shortest_path(graph, src, dest):
if src == dest:
return [src], 0
dist = traverse(graph, Heap([([src], 0)], cmp_frontier), dest)
if not dist:
print "No path form %s to %s" % (src, dest)
return
print "The min distance from %s to %s is %s" % (src, dest, dist)
return dist
def __init__(self, **kwargs):
""" Initialize the Queue """
list = kwargs.get('list', [])
cmprator = kwargs.get('cmprator',
lib.utils.get_def_cmprator())
self._debug = kwargs.get('debug', 0)
self.elem_key_handler = kwargs.get('elem_key_handler',
self.def_elem_key_handler)
self.id_to_idx_map = {}
self.heap = Heap(
list = list,
cmprator = cmprator,
debug = self._debug
)
class Max_Pri_Queue:
def def_elem_key_handler(self, elem):
return elem
def __init__(self, **kwargs):
""" Initialize the Queue """
list = kwargs.get('list', [])
cmprator = kwargs.get('cmprator',
lib.utils.get_def_cmprator())
self._debug = kwargs.get('debug', 0)
self.elem_key_handler = kwargs.get('elem_key_handler',
self.def_elem_key_handler)
self.id_to_idx_map = {}
self.heap = Heap(
list = list,
cmprator = cmprator,
debug = self._debug
)
@property
def debug(self):
return self._debug
def maximum(self):
""" Find elem whose key has max val in the queue """
if not self.heap.heapsize > 0:
raise ex.exceptions.HeapSizeZero("Heap empty")
return self.heap.read(0)
def update_id_idx_map(self, start_idx = 0):
""" Update the internal id to heap index map """
heapsize = self.heap.heapsize
if not start_idx <= heapsize:
raise ex.exceptions.BadIndexAccess(
"Cannot go beyond heapsize idx " + str(heapsize)
)
curr_idx = start_idx
while curr_idx < heapsize:
curr_id = self.heap.read(curr_idx)
self.id_to_idx_map[curr_id] = curr_idx
curr_idx += 1
return True
def swap_nodes(self, idx1, idx2):
""" Swap heap nodes """
tmp = self.heap.read(idx1)
self.heap.write(idx1, self.heap.read(idx2))
self.heap.write(idx2, tmp)
id1 = self.heap.read(idx1)
id2 = self.heap.read(idx2)
self.id_to_idx_map[id1] = idx1
self.id_to_idx_map[id2] = idx2
return True
def update_key(self, id, new_key, op = 'inc'):
""" Update key of element from k to new_k
provided k > new_k """
# cannot increase key if heap empty
idx = self.id_to_idx_map[id]
heapsize = self.heap.heapsize
if not heapsize > 0:
raise ex.exceptions.HeapSizeZero("Heap empty")
if not idx < heapsize:
raise ex.exceptions.BadIndexAccess(
"Accessing - [" + str(idx) + "] > " +\
"heapsize idx " + str(heapsize - 1)
)
# check if heap property violated - if it is - fix it
if op == 'inc':
parent_idx = self.heap.get_parent_idx(idx)
cmprator_out = self.heap.cmprator(
self.heap.read(idx),
self.heap.read(parent_idx)
)
while (cmprator_out > 0 and idx >= 0):
self.swap_nodes(idx, parent_idx)
idx = parent_idx
parent_idx = self.heap.get_parent_idx(idx)
cmprator_out = self.heap.cmprator(
self.heap.read(idx),
self.heap.read(parent_idx)
)
else:
self.heap.max_heapify(idx)
self.update_id_idx_map(idx)
return True
def insert(self, id):
""" Insert a new element in the queue """
if id in self.id_to_idx_map:
raise ex.exceptions.DupElemInsertion(
"Id " + str(id) + " already exists in queue"
)
self.heap.inc_heapsize(1)
heap_new_idx = self.heap.heapsize - 1
self.heap.write(heap_new_idx, id)
self.update_id_idx_map(heap_new_idx)
self.update_key(id, self.elem_key_handler(id))
return True
def extract_max(self):
""" Remove and return elem whose key has max val in queue """
try:
max = self.maximum()
except ex.exceptions.HeapError as e:
raise \
ex.exceptions.HeapError("Cannot extract max - " +\
e.message)
self.swap_nodes(0, self.heap.heapsize - 1)
self.heap.dec_heapsize(1)
self.heap.max_heapify()
self.update_id_idx_map()
return max
def get_iter(self):
i = 0
max = self.heap.heapsize
while i < max:
yield self.heap.read(i)
i += 1
def flush(self):
count = 0
while self.heap.heapsize > 0:
self.extract_max()
count += 1
return count
def __init__(self):
self.lowers = Heap(is_max=True) # max heap for lower half
self.highers = Heap(is_max=False) # min heap for higher half
class Solution():
def __init__(self):
self.lowers = Heap(is_max=True) # max heap for lower half
self.highers = Heap(is_max=False) # min heap for higher half
def get_medians(self, source):
medians = []
for item in source:
self.add_item(item)
self.rebalance()
medians.append(self.get_median())
return medians
def add_item(self, item):
if self.lowers.size() == 0 or item < self.lowers.peek():
self.lowers.add(item)
else:
self.highers.add(item)
def rebalance(self):
bigger_heap = self.lowers if self.lowers.size() > self.highers.size(
) else self.highers
smaller_heap = self.highers if self.lowers.size() > self.highers.size(
) else self.lowers
if bigger_heap.size() - smaller_heap.size() >= 2:
smaller_heap.add(bigger_heap.pop())
def get_median(self):
bigger_heap = self.lowers if self.lowers.size() > self.highers.size(
) else self.highers
smaller_heap = self.highers if self.lowers.size() > self.highers.size(
) else self.lowers
if bigger_heap.size() == smaller_heap.size():
return (bigger_heap.peek() + smaller_heap.peek()) / 2
else:
return bigger_heap.peek()
