棧 用python實現棧

分別採用有序列表、單向鏈和雙向鏈實現棧的推入、彈出等功能。

方法一：有序列表的實現

# 直接利用python內建的list實現

class
stack
(object):
def__init__
(self)
:        self.stack =
defpush
(self, item)
:def
peek
(self)
:if self.isempty():
raise indexerror(
"peek from empty stack"
)return self.stack[-1
]def
pop(self)
:if self.isempty():
raise indexerror(
"pop from empty stack"
)return self.stack.pop(
)def
isempty
(self)
:return self.stack ==
def__len__
(self)
:return
len(self.stack)

class

node
(object):
def__init__
(self, value)
:        self.value = value
self.
next
=none
def__repr__
(self)
:return self.value
class
stack
(object):
def__init__
(self)
:        self.head =
none
defpush
(self, value)
:        node = node(value)
if self.head is
none
:            self.head = node
else
:            node.
next
= self.head
self.head = node
defpop(self)
:if self.isempty():
raise indexerror(
"pop from empty stack"
)else
:            node = self.head.value
self.head = self.head.
next
return node
defpeek
(self)
:if self.isempty():
raise indexerror(
"peek from empty stack"
)else
:return self.head.value
defisempty
(self)
:return self.head is
none
def__len__
(self)
:        length =
0        current = self.head
while current:
length +=
1            current = current.
next
return length

class

node
(object):
def__init__
(self, value, prev=
none
,next
=none):
self.value = value
self.prev = prev
self.
next
=next
def__repr__
(self)
:return self.value
class
stack
(object):
def__init__
(self)
:        self.head =
none
defpush
(self, value)
:        new_node = node(value)
if self.isempty():
self.head = new_node
else
:            new_node.
next
= self.head
self.head.prev = new_node
self.head = new_node
defpop(self)
:if self.isempty():
raise indexerror(
"pop from empty stack"
)else
:            current = self.head
if current.
next
isnone
:                self.head =
none
else
:                current.
next
.prev =
none
self.head = current.
next
return current.value
defpeek
(self)
:if self.isempty():
raise indexerror(
"peek from empty stack"
)else
:return self.head
def__len__
(self)
:        length =
0        current = self.head
while current:
length +=
1            current = current.
next
return length
defisempty
(self)
:return self.head is
none

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