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executable file
·153 lines (123 loc) · 3.81 KB
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# This file contains two
# implementations of priority queues:
# 1, as sorted list
# 2, as heap stored in a list
# and in addition,
# an implementation of heap sort function
class PrioQueueError(ValueError):
pass
class PrioQue(object):
""" Implementing binary trees as sorted list
"""
def __init__(self, elist=[]):
self.elems = list(elist)
self.elems.sort()
def is_empty(self):
return self.elems == []
def peek(self):
if self.is_empty():
raise PrioQueueError("in top")
return self.elems[len(self.elems) - 1]
def dequeue(self):
if self.is_empty():
raise PrioQueueError("in pop")
return self.elems.pop()
def enqueue(self, e):
i = len(self.elems) - 1
while i >= 0:
if self.elems[i] <= e:
i -= 1
else:
break
self.elems.insert(i + 1, e)
class PrioQueue(object):
""" Implementing binary trees as heaps
"""
def __init__(self, elist=[]):
self.elems = list(elist)
if elist != []:
self.buildheap()
def __repr__(self):
return '; '.join(str(i) for i in self.elems)
def is_empty(self):
return self.elems == []
def peek(self):
if self.is_empty():
raise PrioQueueError("in top")
return self.elems[0]
def enqueue(self, e):
self.elems.append(None) # add a dummy element
self.siftup(e, len(self.elems) - 1)
def siftup(self, e, last):
elems, i, j = self.elems, last, (last - 1) // 2
while i > 0 and e < elems[j]:
elems[i] = elems[j]
i, j = j, (j - 1) // 2
elems[i] = e
def dequeue(self):
if self.is_empty():
raise PrioQueueError("in pop")
elems = self.elems
e0 = elems[0]
e = elems.pop()
if len(elems) > 0:
self.siftdown(e, 0, len(elems))
return e0
def siftdown(self, e, begin, end):
elems, i, j = self.elems, begin, begin * 2 + 1
while j < end: # invariant: j == 2*i+1
if j + 1 < end and elems[j + 1] < elems[j]:
j += 1 # elems[j] <= its brother
if e < elems[j]: # e is the smallest of the three
break
elems[i] = elems[j] # elems[j] is the smallest, move it up
i, j = j, 2 * j + 1
elems[i] = e
def buildheap(self):
end = len(self.elems)
for i in range(end // 2, -1, -1):
self.siftdown(self.elems[i], i, end)
def heap_sort(elems):
def siftdown(elems, e, begin, end):
i, j = begin, begin * 2 + 1
while j < end: # invariant: j == 2*i+1
if j + 1 < end and elems[j + 1] < elems[j]:
j += 1 # elems[j] <= its brother
if e < elems[j]: # e is the smallest of the three
break
elems[i] = elems[j] # elems[j] is the smallest, move it up
i, j = j, 2 * j + 1
elems[i] = e
end = len(elems)
for i in range(end // 2, -1, -1):
siftdown(elems, elems[i], i, end)
for i in range((end - 1), 0, -1):
e = elems[i]
elems[i] = elems[0]
siftdown(elems, e, 0, i)
from random import randint
def test1():
print("Test class PrioQue:")
pq = PrioQue()
for i in range(12):
pq.enqueue(randint(0, 30))
while not pq.is_empty():
print(pq.dequeue())
def test2():
print("Test class PrioQueue:")
pq = PrioQueue()
for i in range(12):
pq.enqueue(randint(0, 30))
while not pq.is_empty():
print(pq.dequeue())
def test3():
print("Test function heap_sort:")
lst = [randint(1, 30) for i in range(15)]
print(lst)
heap_sort(lst)
print(lst)
if __name__ == '__main__':
test1()
test2()
test3()
pass