python代数式括号有效性检验示例代码
思路:
利用栈实现代数式中括号有效行的的检验:
代码:
class mychain(object): #利用链表建立栈,链表为父类
length=0
def __init__(self,value=None,next=None):#创建链表,长度并不包含头部
self.value=value
self.next=next
#mychain.length=mychain.length+1
def append(self,value=None):
while self.next!=None:
self=self.next
self.next=mychain(value)
mychain.length=mychain.length+1 #追加时,链表长度增加
def travle(self):#遍历链表
print(self.value)
if self.next!=None:
self.next.travle()
def drop (self,value):#删除特定值的第一个匹配节点
while self.next!=None:
if self.next.value!=value:
self=self.next
else:
self.next=self.next.next
mychain.length=mychain.length-1 #删除时,链表长度减小
break
def pop(self):#删除未节点
if self.next!=None:#并不删除头结点
while self.next.next!=None:
self=self.next
self.next=None
mychain.length=mychain.length-1#弹出为节点,并减小长度,头结点不弹出
class stock(mychain):#栈类
bottom=None #栈底
top=None #栈顶
n_count=0 #计数
def Max(self): #占中最大值
if self.next!=None:
tmp = self.next.value
while self.next.next!=None:
self=self.next
if self.next.value>tmp:
tmp=self.next.value
return tmp
else:
print('栈为空!')
def Min(self):#栈中的最小值
if self.next!=None:
tmp = self.next.value
while self.next.next!=None:
self=self.next
if self.next.value<tmp:
tmp=self.next.value
return tmp
else:
print('栈为空!')
def push(self,value): #压栈
while self.next != None:
self = self.next
self.next = mychain(value)
stock.top=self.next
stock.length=stock.length+1
stock.n_count=stock.n_count+1
def __init__(self,value='',next=None):
self.value=value
self.next=next
stock.bottom=self
stock.top=self
#stock.n_count=stock.n_count+1
#stock.length=stock.length+1
def append(self,value=''):#取消追加函数
print('请使用Push()!')
def pop(self):
if self.next!=None:#并不删除头结点
while self.next.next!=None:
self=self.next
self.next=None
stock.top=self
stock.length=stock.length-1#弹出为节点,并减小长度,头结点不弹出
class solution(object):
def validationofbrackets(self,astr=''):#检验串中的括号合法性
braketsstock=stock()
for i in astr:
if i in ['{','(','[']:
braketsstock.push(i)
else:
if i==')':
if braketsstock.top.value=='(':
braketsstock.pop()
else:
return False
elif i==']':
if braketsstock.top.value=='[':
braketsstock.pop()
else:
return False
elif i=='}':
if braketsstock.top.value=='{':
braketsstock.pop()
else:
return False
else:
pass
print(astr)
print(braketsstock.length)
if braketsstock.length==0:
return True
else:
return False
运行:
bstr='([{((({{}})))}]){{}}{{}{}{}[][]()(123)(((sin5)))}'
f=solution()
print(f.validationofbrackets(bstr))
总结
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