栈、队列和链表

栈

栈是一种后进先出的策略，其操作包括入栈，出栈，获取栈顶元素值等。

我们这里用python列表简单的模拟栈，考虑上下溢出的情况，其代码实现如下：

class Stack:
def __init__(self,sz=65536):
self.stack = []
self.top = -1
self.size = sz

def isEmpty(self):
return True if self.top is -1 else False

def isFull(self):
return True if self.top is self.size - 1 else False

def push(self,obj): #压入栈操作
if self.isFull():
raise Exception("Stack over flow!")
else:
self.stack.append(obj)
self.top += 1

def pop(self): #弹出栈顶元素
if self.isEmpty():
raise Exception("Stack is empty!")
else:
self.top -= 1
return self.stack.pop()

def count(self): #获取栈中元素个数
return self.top + 1

def top(self): #获取栈顶元素值
if self.isEmpty():
raise Exception("Stack is empty!")
return self.stack[top]

def show(self):
print(self.stack)

队列

队列是一种先进先出的数据结构，主要操作包括入队,出队。入队的元素加入到对尾，从队头取出出队的元素。这里用列表简单模拟队列，其实现如下：

class Queue:
def __init__(self,sz=65535):
self.queue = []
self.size = sz
self.len = 0

def isEmpty(self):
return True if self.len is 0 else False

def isFull(self):
return True if self.len is self.size else False

def length(self):
return self.len

def enqueue(self,obj): #入队
if self.isFull():
raise Exception("Queue is Full!")
else:
self.queue.append(obj)
self.len += 1

def dequeue(self): #出队
if self.isEmpty():
raise Exception("Queue is Empty!")
else:
self.len -= 1
return self.queue.pop(0)

def show(self):
print(self.queue)

实际应用中还使用一种叫做双端队列的数据结构，其实现也在队列的基础上变成可以对两端操作。

class Deque:
def __init__(self,sz=65535):
self.queue = []
self.size = sz
self.len = 0

def isEmpty(self):
return True if self.len is 0 else False

def isFull(self):
return True if self.len is self.size else False

def length(self):
return self.len

def enqueue(self,obj): #从右边入队
if self.isFull():
raise Exception("DeQueue is Full!")
else:
self.len += 1
self.queue.append(obj)

def enqueueLeft(self,obj): #从左边入队
if self.isFull():
raise Exception("DeQueue is Full!")
else:
self.len += 1
self.queue.insert(0,obj)

def dequeue(self): #从左边出队
if self.isEmpty():
raise Exception("DeQueue is Empty!")
else:
self.len -= 1
return self.queue.pop(0)

def dequeueRight(self): #从右边出队
if self.isEmpty():
raise Exception("DeQueue is Empty!")
else:
self.len -= 1
return self.queue.pop()

def show(self):
print(self.queue)

链表

链表分为单向链表和双向链表，这里给出双向链表的实现：

#构成双向链表的结点
class Node:
def __init__(self,key=None):
self.key = key
self.prev = None #指向前驱
self.next = None #指向后继

def getKey(self):
return self.key

def getPrev(self):
return self.prev

def getNext(self):
return self.next

def setKey(self, key):
self.key = key

def setPrev(self, prev):
self.prev = prev

def setNext(self, next):
self.next = next

class LinkList:
def __init__(self,data=None):
self.head = None
self.len = 0
if data:
p = self.head = Node(data[0])
self.len += 1
for key in data[1:]:
node = Node(key)
p.setNext(node)
node.setPrev(p)
self.len += 1
p = node
#重载[]运算符，使其具体下标访问能力，比如像obj[1]这样访问
def __getitem__(self, index):
if index >= self.len or index < 0:
raise Exception("Index out of range!")
else:
p = self.head
for i in range(index):
p = p.getNext()
return p.getKey()

def length(self):
return self.len

def search(self,key):
p = self.head
while p and p.getKey() is not key:
p = p.getNext()
return p

def insert(self,key):
p = Node(key)
if not self.head:
self.head = p
self.len += 1
else:
self.head.setPrev(p)
p.setNext(self.head)
self.head = p
self.len += 1

def delete(self,key):
p = self.search(key)
if p:
if p.getPrev():
p.getPrev().setNext(p.getNext())
else:
self.head = p.getNext()
if p.getNext():
p.getNext().setPrev(p.getPrev())
p.setPrev(None)
p.setNext(None)
self.len -= 1

def show(self):
p = self.head
while p:
print(p.getKey(),end=' ')
p = p.getNext()
print()