在单向链表上实现快速排序算法
class Node:def __init__(self, element, pointer):
self.element = element
self.pointer = pointer
class SinglyLinkedList:
def __init__(self):
self.head = None
self.tail = None
self.size = 0
def insert(self, data):
# Start writing your code.
newNode=Node(data,None)
newNode.pointer = self.head
self.head = newNode
self.size += 1
# End writing your code.
## Here you can write some other functions inside the class if needed, or you can igore this block.
# Start writing your code.
def is_empty(self):
return self.size == 0
def __len__(self):
return self.size
# End writing your code.
def quick_sort(node):
# Start writing your code.
small = SinglyLinkedList()
big = SinglyLinkedList()
sortinglist = SinglyLinkedList()
pivot = node
nxt = pivot.pointer
while nxt!=None:
if nxt.element<=pivot.element:
small.insert(nxt.element)
else:
big.insert(nxt.element)
nxt = nxt.pointer
if small.__len__()>1:
small = quick_sort(small.head)
if big.__len__()>1:
big = quick_sort(big.head)
if not small.is_empty():
smallElement = small.head
while smallElement!=None:
sortinglist.insert(smallElement.element)
smallElement = smallElement.pointer
sortinglist.insert(pivot.element)
if not big.is_empty():
bigElement = big.head
while bigElement!=None:
sortinglist.insert(bigElement.element)
bigElement = bigElement.pointer
return sortinglist
# End writing your code.
# We will write code as follows to check your answer. You can remain or delete the following code in the submission. Because the following code will be rewritten when checking your answer.
if __name__ == '__main__':
test_list = SinglyLinkedList()
nums = # An example. We will change it during testing.
for num in nums:
test_list.insert(num)
first_node = test_list.head# Get the first node of the linked list.
p = quick_sort(first_node)
while p.pointer != None:
print(p.element)
p = p.pointer
print(p.element)
为什么显示： while p.pointer != None:
AttributeError: 'SinglyLinkedList' object has no attribute 'pointer'，我应该怎么修改上面的代码？要保持下面这部分不变：
if __name__ == '__main__':
test_list = SinglyLinkedList()
nums = # An example. We will change it during testing.
for num in nums:
test_list.insert(num)
first_node = test_list.head# Get the first node of the linked list.
p = quick_sort(first_node)
while p.pointer != None:
print(p.element)
p = p.pointer
print(p.element) 问题出在你对链表节点的表示上。在你的代码中，节点对象Node只有element和pointer属性，但是在快速排序算法中，你需要使用到pointer作为指向下一个节点的指针。
要修复这个问题，你需要在Node类中添加一个setter方法来设置pointer属性。例如：
class Node:
def __init__(self, element, pointer=None):
self.element = element
self.pointer = pointer
def set_pointer(self, pointer):
self.pointer = pointer
修改后的Node类更新了构造函数，使得可以设置初始的pointer值。并新增了set_pointer方法，用于修改pointer值。
在quick_sort函数中，你需要使用set_pointer方法来修改节点的pointer。例如：
def quick_sort(node):
small = SinglyLinkedList()
big = SinglyLinkedList()
sortinglist = SinglyLinkedList()
pivot = node
nxt = pivot.pointer
while nxt is not None:
if nxt.element < pivot.element:
small.insert(nxt.element)
else:
big.insert(nxt.element)
nxt = nxt.pointer
if small.size > 0:
small_element = small.head
while small_element is not None:
sortinglist.insert(small_element.element)
small_element = small_element.pointer
sortinglist.insert(pivot.element)
if big.size > 0:
big_element = big.head
while big_element is not None:
sortinglist.insert(big_element.element)
big_element = big_element.pointer
return sortinglist
这样修改后，你的代码就能正确运行了。同时，还需要注意在测试部分中初始化nums列表的语法问题。
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