我正在尝试在python中实现循环队列(没有有限的缓冲区(。 当我在enqueue后打电话给display时，它不起作用。但是，在其他情况下调用时，它可以正常工作。
它的实现类似于按预期工作的get_size函数。
以下是实现：
class Node(object):
def __init__(self, value):
self.value = value
self.next = None
class LinkedCircularQueue(object):
def __init__(self, head=None, tail=None):
self.head = head
self.tail = tail
def enqueue(self, item):
"""
Add the node to the back of the queue and set its next pointer to
self.head
"""
if self.tail is not None:
self.tail.next = item
else:
self.head = item
self.tail = item
item.next = self.head
return self.tail.value
def dequeue(self):
"""
Remove the oldest node (from the front) by copying the value and
making the preceding node as the new head
"""
if self.head is not None:
deleted = self.head.value
self.head = self.head.next
else:
deleted = None
print("Circular queue is empty !!")
return deleted
def display(self):
"""
Traverse from front to back and show elements
"""
front = self.head
back = self.tail
if front is not None and back is not None:
while back.next != front:
print(front.value, end=" ")
front = front.next
else:
print("Circular queue is empty !!")
def get_size(self):
"""
Traverse from front to back and count elements
"""
size = 0
if self.head is not None and self.tail is not None:
while self.tail.next != self.head:
size += 1
self.head = self.head.next
return size
def peek_front(self):
front = self.head
return front.value
def peek_back(self):
back = self.tail
return back.value
def is_empty(self):
first = self.head
last = self.tail
if first is None and last is None:
return True
else:
return False
def main():
# Initialize elements
element1 = Node(1)
element2 = Node(2)
element3 = Node(3)
element4 = Node(4)
element5 = Node(5)
linked_circular_queue = LinkedCircularQueue()
# Initial tests
linked_circular_queue.display()
print(linked_circular_queue.is_empty())
print(linked_circular_queue.get_size())
print()
# Test enqueue
linked_circular_queue.enqueue(element5)
linked_circular_queue.enqueue(element3)
linked_circular_queue.enqueue(element1)
linked_circular_queue.enqueue(element4)
linked_circular_queue.enqueue(element2)
linked_circular_queue.display() # doesn't work
print()
# Test dequeue
linked_circular_queue.dequeue()
linked_circular_queue.dequeue()
linked_circular_queue.display()
print()
# Test peek
print(linked_circular_queue.peek_front())
print(linked_circular_queue.peek_back())
print()
# Final tests
print(linked_circular_queue.is_empty())
print(linked_circular_queue.get_size())
if __name__ == '__main__':
main()
电流输出：
Circular queue is empty !!
True
0
1 4 2
1
2
False
3
预期输出：
Circular queue is empty !!
True
0
5 3 1 4 2
1 4 2
1
2
False
3
将 while 循环从display函数更改为：
while back != front:
print(front.value, end=" ")
front = front.next
print(back.value) # print(front.value) also works