python-数据结构代码 栈

from pythonds.basic.stack import Stack

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="({["
    closers=")}]"
    return opens.index(open)==closers.index(close)

def divideBy2(decNumber):
    remstack = Stack()
    while decNumber > 0:
        rem = decNumber % 2
        remstack.push(rem)
        decNumber = decNumber // 2
    binString = ""
    while not remstack.isEmpty():
        binString = binString + str(remstack.pop())

    return binString

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 newString

def infixToPostfix(infixexpr):
    prec={}
    prec["*"]=3
    prec["/"]=3
    prec["+"]=2
    prec["-"]=2
    prec["("]=1
    opStack = Stack()
    postfixList=[]
    tokenList=infixexpr.split()
    print(tokenList)
    for token in tokenList:
        if token in "ABCDEFGHIJKLMNOPQRSTUVWXYZ" or token in "0123456789":
            postfixList.append(token)
        elif token == "(":
            opStack.push(token)
        elif token == ")":
            topToken = opStack.pop()
            while topToken != "(":
                postfixList.append(topToken)
                topToken = opStack.pop()
        else:
            while (not opStack.isEmpty()) and 
                (prec[opStack.peek()] >= prec[token]):
                postfixList.append(opStack.pop())
            opStack.push(token)
    while not opStack.isEmpty():
        postfixList.append(opStack.pop())
    return " ".join(postfixList)

def postfixEval(postfixExpr):
    operandStack = Stack()
    tokenList = postfixExpr.split()
    for token in tokenList:
        if token in "0123456789":
            operandStack.push(int(token))
        else:
            operand2 = operandStack.pop()
            operand1 = operandStack.pop()
            result = doMath(token,operand1,operand2)
            operandStack.push(result)
    return operandStack.pop()

def doMath(op,op1,op2):
    if op == "*":
        return op1 * op2
    elif op == "/":
        return op1 / op2
    elif op == "+":
        return op1 + op2
    else:
        return op1 - op2

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)