python - python中的单链表反向

Question

我正在尝试在 python 中创建一个简单的单链表。(我知道不需要在Python中实现列表，但这不是重点)

这是我的代码:

class Node:
    def __init__(self,data):
        self.data = data
        self.next= None



class List:
    def __init__(self):
        self.firstNode = Node(None)

    def inserthead(self,newnode):
        if not self.firstNode.next:
            newnode.next = None
            self.firstNode.next = newnode
        else:
            newnode.next = self.firstNode.next
            self.firstNode.next= newnode


    def __show(self,start):
        if start.next:
            print start.data
            self.__show(start.next)

    def printlist(self):
        self.__show(self.firstNode)

    def __reverte_recursive(self,node):
        temp = None
        if not node.next: return node
        else:
            temp = self.__reverte_recursive(node.next)
            node.next.next= node
            node.next = None
        return temp

    def reverte_list1(self):
        self.firstNode=self.__reverte_recursive(self.firstNode)

    def __reverte_iterative(self,node):
        temp = None
        previous = None
        while node and node.next:
            temp = node.next
            node.next= previous
            previous = node
            node = temp
        return previous
    def reverte_iterative(self):
        self.firstNode=self.__reverte_iterative(self.firstNode)

nodeA = Node("A")
nodeB = Node("B")
nodeC = Node("C")
nodeD = Node("D")
nodeE = Node("E")


list1= List()

list1.inserthead(nodeA)
list1.inserthead(nodeB)
                           class Node:
    def __init__(self,data):
        self.data = data
        self.next= None



class List:
    def __init__(self):
        self.firstNode = Node(None)

    def inserthead(self,newnode):
        if not self.firstNode.next:
            newnode.next = None
            self.firstNode.next = newnode
        else:
            newnode.next = self.firstNode.next
            self.firstNode.next= newnode


    def __show(self,start):
        if start.next:
            print start.data
            self.__show(start.next)

    def printlist(self):
        self.__show(self.firstNode)

    def __reverte_recursive(self,node):
        temp = None
        if not node.next: return node
        else:
            temp = self.__reverte_recursive(node.next)
            node.next.next= node
            node.next = None
        return temp

    def reverte_list1(self):
        self.firstNode=self.__reverte_recursive(self.firstNode)

    def __reverte_iterative(self,node):
        temp = None
        previous = None
        while node and node.next:
            temp = node.next
            node.next= previous
            previous = node
            node = temp
        return previous
    def reverte_iterative(self):
        self.firstNode=self.__reverte_iterative(self.firstNode)

nodeA = Node("A")
nodeB = Node("B")
nodeC = Node("C")
nodeD = Node("D")
nodeE = Node("E")


list1= List()

list1.inserthead(nodeA)
list1.inserthead(nodeB)
list1.inserthead(nodeC)
list1.inserthead(nodeD)
list1.inserthead(nodeE)


print "list"
list1.printlist()
print "list reverse"
list1.reverte_list1()
list1.printlist()
list1.reverte_iterative()
print "list reverse reverse"
list1.printlist()

结果如下:

None
E
D
C
B
list reverse
A
B
C
D
E
list reverse reverse
E
D
C
B

由于某种原因，我无法打印所有列表，并且在第一种情况下不打印“A”节点但打印第一个节点(但我检查过并且 B 节点指向 A)第一个反向就OK了但第三个同样不打印 A 节点，即使它是由 B 节点指向的。打印的问题可能出在 __show 函数中。但我想我是一个概念错误。

谢谢

Answer 1

def __show(self,start):
   if start.next:
       print start.data
       self.__show(start.next)

仅在有下一个节点时才打印当前节点，这就是为什么最后一个节点永远不会被打印的原因。应该是:

def __show(self,start):
   if start:
       print start.data
       self.__show(start.next)

您在整个代码中检查/分配节点而不是下一个节点时犯了类似的错误，反之亦然(例如在 inserthead() 中 - 这导致 None正在打印)