i'm trying to create a simple single linked list in python. (i know there is no need to implement list in python, but that's not the point)
here is my code:
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()
and there are the result:
None
E
D
C
B
list reverse
A
B
C
D
E
list reverse reverse
E
D
C
B
for some reason i can't print all the list and in the first case doesn't print the "A" Node but print the first node(but i checkd and the B node points to A) the first reverse is OK but the third again don't print the A node even if it's pointed by the B Node. probably the problem of the printing is in the __show function. but i suppose ia conceptual bug.
thanks
def __show(self,start):
if start.next:
print start.data
self.__show(start.next)
that only prints the current node if it has a next node, thats why the last node is never printed. should be:
def __show(self,start):
if start:
print start.data
self.__show(start.next)
you make similar mistakes of checking/assigning a node instead of it's next and vice versa throughout the code (in inserthead()
for example - which is causing the None
being printed)
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