class Node:
def __init__(self, value):
self.value = value
self.next = None
def __str__(self):
return "Node({})".format(self.value)
__repr__ = __str__
class Queue:
def __init__(self):
#Constructor take head and tail
self.head=None
self.tail=None
def __str__(self):
#proper format
temp=self.head
out=[]
while temp:
out.append(str(temp.value))
temp=temp.next
out=' '.join(out)
return ('Head:{}\nTail:{}\nQueue:{}'.format(self.head,self.tail,out))
__repr__=__str__
def isEmpty(self):
#check if the queue is empty
return (self.head == None)
def len(self):
#check the length of queue
current = self.head
len = 0
while current != None:
len += 1
current = current.next
return len
def enqueue(self, value):
#add a node to the end of queue
node = Node(value)
if self.isEmpty():
self.head = node
self.tail = node
else:
self.tail.next = node
self.tail = node
def dequeue(self):
#delete a node from the beginning of queue
if self.isEmpty():
return 'Queue is empty'
elif (self.head == self.tail):
pop = self.head.value
self.head = None
self.tail = None
return pop
else:
popped = self.head.value
self.head = self.head.next
return popped
def peek(self):
#show the first node
return self.head.value
class QueueTower:
def __init__(self, numDisks, A=Queue(), B=Queue(), C= Queue()):
self.numDisks = numDisks
self.A = Queue()
self.B = Queue()
self.C = Queue()
for i in range(numDisks, 0, -1):
self.A.enqueue(i)
#print(i)
def reversequeue(self, q):
#reverse the queue without using stack
if q.isEmpty() == False:
data = q.peek()
q.dequeue()
q = self.reversequeue(q) #recurssion
q.enqueue(data)
return q
return Queue()
def validMove(self, a, b):
if not a.len():
c = self.reversequeue(b)
a.enqueue(c.dequeue())
b.dequeue()
elif not b.len():
d = self.reversequeue(a)
b.enqueue(d.dequeue())
a.dequeue()
elif a.peek() > b.peek():
e = self.reversequeue(b)
a.enqueue(e.dequeue())
b.dequeue()
else:
f = self.reversequeue(a)
b.enqueue(f.dequeue())
a.dequeue()
def hanoi(self, n):
if n%2 == 0:
self.B, self.C = self.C, self.B
move = 2**n
for i in range(1, move):
if i%3==1:
self.validMove(self.A, self.C)
if i%3==2:
self.validMove(self.A, self.B)
if i%3==0:
self.validMove(self.B, self.C)
print("rod " + str(self.A)+ " has " + str(self.A.len()), "rod B " + str(self.B.len()), "rod C "+ str(self.C.len()))
print("move needed is " + str(move-1))
tower1 = QueueTower(3)
tower1.hanoi(3)
代码没有错误，但是没有给我正确的输出。我在一张纸上写下了逻辑，似乎可以正常工作。但是，当我实现它时，它没有给我正确的输出。输出最终显示我在塔B和塔C中只有一个磁盘，但在塔A中没有磁盘。 请帮助我理解问题。
非常感谢您的帮助！
答案 0 :(得分：1)
您的反向排队方法返回错误的值。
class Node:
def __init__(self, value):
self.value = value
self.next = None
def __str__(self):
return "Disc({})".format(self.value)
class Queue:
def __init__(self, name):
self.name = name
self.head = None
self.tail = None
def is_empty(self):
return self.head is None
def len(self):
current = self.head
len = 0
while current is not None:
len += 1
current = current.next
return len
def enqueue(self, value):
node = Node(value)
if self.is_empty():
self.head = node
self.tail = node
else:
self.tail.next = node
self.tail = node
def dequeue(self):
if self.is_empty():
return "EMPTY"
elif self.head == self.tail:
help = self.head.value
self.head = None
self.tail = None
return help
else:
jump = self.head.value
self.head = self.head.next
return jump
def peek(self):
return self.head.value
class QueueTower:
def __init__(self, number_of_discs):
self.number_of_discs = number_of_discs
self.A, self.B, self.C = Queue("A"), Queue("B"), Queue("C")
for i in range(number_of_discs, 0, -1):
self.A.enqueue(i)
def reverse_queue(self, q):
if not q.is_empty():
if q.head != q.tail:
data = q.peek()
q.dequeue()
self.reverse_queue(q) # recursion
q.enqueue(data)
return q
else:
data = q.peek()
q.dequeue()
q.enqueue(data)
return q
return Queue(q.name)
def valid_move(self, a, b):
if not a.len():
a.enqueue(b.dequeue())
elif not b.len():
if a.len() == self.number_of_discs:
d = self.reverse_queue(a)
else:
d = a
b.enqueue(d.dequeue())
elif a.peek() > b.peek():
e = b
a = self.reverse_queue(a)
a.enqueue(e.peek())
self.reverse_queue(a)
b.dequeue()
else:
b = self.reverse_queue(b)
b.enqueue(a.dequeue())
self.reverse_queue(b)
def hanoi(self, n):
if n % 2 == 0:
self.B, self.C = self.C, self.B
move = 2 ** n
for i in range(1, move):
if i % 3 == 1:
self.valid_move(self.A, self.C)
if i % 3 == 2:
self.valid_move(self.A, self.B)
if i % 3 == 0:
self.valid_move(self.B, self.C)
# Start formatting output.
tower_a, tower_b, tower_c = self.A, self.B, self.C
if n % 2 == 0:
tower_b, tower_c = self.C, self.B
for j in [tower_a, tower_b, tower_c]:
print("\n |", j.name, "|", end=" ")
current = j.head
while current:
print(current, "|", end=" ")
current = current.next
print()
# End formatting output.
print("\nMove needed is: " + str(move - 1))
tower = QueueTower(3)
tower.hanoi(3)
输出：
| A | Disc(2) | Disc(3) |
| B |
| C | Disc(1) |
| A | Disc(3) |
| B | Disc(2) |
| C | Disc(1) |
| A | Disc(3) |
| B | Disc(1) | Disc(2) |
| C |
| A |
| B | Disc(1) | Disc(2) |
| C | Disc(3) |
| A | Disc(1) |
| B | Disc(2) |
| C | Disc(3) |
| A | Disc(1) |
| B |
| C | Disc(2) | Disc(3) |
| A |
| B |
| C | Disc(1) | Disc(2) | Disc(3) |
Move needed is: 7