栈Stack:

一种有次序的数据集合，在栈中，数据项的加入和移除都

仅发生在同一端

一端叫栈‘顶top‘，另一端叫栈’底base‘

每个数据顶仅从’栈顶‘一端加入数据集中，从数据集中移除；

栈具有后进先出LIFO的特性

class Stack:    def __init__(self):        self.items = []    def isEmpty(self):        return self.items == []    def push(self,item):        self.items.append(item)    def pop(self):        return self.items.pop()    def peek(self):        return self.items[len(self.items)-1]    def size(self):        return len(self.items)    s = Stack()print(s.isEmpty())s.push(4)s.push('dog')print(s.peek())

1）问题：判断‘（）’是不是成对

def parChecker(symbolString):#判断（）是否成对    s = Stack()    balanced = True    index = 0    while index <len(symbolString) and balanced:        symbol = symbolString[index]        if symbol =='(':            s.push(symbol)        else:            if s.isEmpty():                balanced = True            else:                s.pop()    index = index +1        if balanced and s.isEmpty():        return True    else:        return False    print(parChecker('((())'))    

2）问题：{{([])}}不同类型的括号匹配

def parChecker(symbolString):    s = Stack()    balanced = True    index =0    while index <len(symbolString)and balanced:        symbol = symbolString[index]        if symbol in '([{':            s.push(symbol)        else:            if s.isEmpty():                balanced =False            else:                top = s.pop()                if not matches(top,symbol):                    balanced = False        index = index+1    if balanced and s.isEmpty():        return True    else:        return False    def matches(open,close):    opens ='([{'    closes=')]}'    return opens.index(open) ==closes.index(close)print(parChecker('{{([][])}}'))

3）十进制转二进制

def divideBy2(decNumber):    remstack = Stack()        while decNumber>0:        rem =decNumber%2#求余数        remstack.push(rem)        decNumber =decNumber//2#整数除    binString =''    while not remstack.isEmpty():        binString =binString + str(remstack.pop())    return binStringprint(divideBy2(16))

4）十进制转其他进制

def baseConverter(decNumber,base):    digits = '0123456789ABCDEF'    remstack = Stack()    while decNumber>0:        rem = decNumber%base        remstack.push(rem)        decNumber = decNumber//base    newString =''    while not remstack.isEmpty():        newString = newString +digits[remstack.pop()]    return newStringprint(baseConverter(25, 2))print(baseConverter(25, 16))