python-student-support-code/priority_queue.py at main · IUCompilerCourse/python-student-support-code · GitHub

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classPriorityQueue:
def__init__(self, less):
self.heap=Heap([], less, update_position)
self.get_key_and_pos= {}

def__repr__(self):
returnrepr(self.heap)

defpush(self, key):
kp=KeyWithPosition(key)
self.get_key_and_pos[key] =kp
self.heap.insert(kp)

defpop(self):
returnself.heap.extract_max().key

defincrease_key(self, key):
obj=self.get_key_and_pos[key]
heap_increase_key(self.heap, obj.position)

defempty(self):
returnself.heap.heap_size==0

classKeyWithPosition:
def__init__(self, k):
self.key=k
self.position=-1

def__repr__(self):
returnstr(self.key) +'@'+repr(self.position)

defupdate_position(key_with_pos, pos):
key_with_pos.position=pos

classHeap:
def__init__(self, data, less, update):
self.data=data
self.less=less
self.update=update
i=0
forobjinself.data:
self.update(obj, i)
i+=1
build_max_heap(self)

def__repr__(self):
returnrepr(self.data[:self.heap_size])

defmaximum(self):
returnself.data[0]

definsert(self, obj):
self.heap_size+=1
iflen(self.data) <self.heap_size:
self.data.append(obj)
else:
self.data[self.heap_size-1] =obj
self.update(obj, self.heap_size-1)
heap_increase_key(self, self.heap_size-1)

defextract_max(self):
assertself.heap_size!=0
max=self.data[0]
self.data[0] =self.data[self.heap_size-1]
self.update(self.data[0], 0)
self.heap_size-=1
max_heapify(self, 0)
returnmax

defleft(i):
return2*i+1

defright(i):
return2* (i+1)

defparent(i):
return (i-1) //2

defswap(A, i, j):
tmp=A[i]
A[i] =A[j]
A[j] =tmp

defheap_increase_key(H, i):
whilei>0andH.less(H.data[parent(i)], H.data[i]):
swap(H.data, i, parent(i))
H.update(H.data[i], i)
H.update(H.data[parent(i)], parent(i))
i=parent(i)

defmax_heapify(H, i):
l=left(i)
r=right(i)
ifl<H.heap_sizeandH.less(H.data[i], H.data[l]):
largest=l
else:
largest=i
ifr<H.heap_sizeandH.less(H.data[largest], H.data[r]):
largest=r
iflargest!=i:
swap(H.data, i, largest)
H.update(H.data[i], i)
H.update(H.data[largest], largest)
max_heapify(H, largest)

defbuild_max_heap(H):
H.heap_size=len(H.data)
last_parent=len(H.data) //2
foriinrange(last_parent, -1, -1):
max_heapify(H, i)

defheap_sort(H):
build_max_heap(H)
foriinrange(len(H.data)-1, 0, -1):
swap(H.data, 0, i)
H.update(H.data[0], 0); H.update(H.data[i], i)
H.heap_size-=1
max_heapify(H, 0)

defless(x, y):
returnx<y

defignore_update(obj, pos):
pass

if__name__=="__main__":
# test Heap build and extract_max
L= [4,3,5,1,2]
h=Heap(L, less, ignore_update)
foriinrange(5, 0, -1):
asserth.extract_max() ==i

# test Heap insert
L= [4,3,5,1,2]
forkinL:
h.insert(k)
foriinrange(5, 0, -1):
asserth.extract_max() ==i

# test heap_sort
L= [4,3,5,1,2]
h=Heap(L, less, ignore_update)
heap_sort(h)
foriinrange(0, 5):
assertL[i] ==i+1

# test PriorityQeueue push and pop
L= {'a': 4, 'b': 3, 'c':5,'d':1,'e':2}
defless(x, y):
returnL[x.key] <L[y.key]
Q=PriorityQueue(less)
fork, vinL.items():
Q.push(k)
P= ['c', 'a', 'b', 'e', 'd']
foriinrange(0, len(P)):
assertQ.pop() ==P[i]

# test increase_key
Q=PriorityQueue(less)
fork, vinL.items():
Q.push(k)
fork, vinL.items():
L[k] =v+2
Q.increase_key(k)
foriinrange(5, 0, -1):
k=Q.pop()
assertL[k] ==i+2

print('passed all tests')