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
