二叉树解析数学表达式

from pythonds.basic.stack import Stack

from pythonds.trees.binaryTree import BinaryTree

def buildParseTree(fpexp):

    fplist = fpexp.split()

    pStack = Stack()

    eTree = BinaryTree('')

    pStack.push(eTree)

    currentTree = eTree

    for i in fplist:

        if i == '(':

            currentTree.insertLeft('')

            pStack.push(currentTree)

            currentTree = currentTree.getLeftChild()

        elif i not in ['+', '-', '*', '/', ')']:

            currentTree.setRootVal(int(i))

            parent = pStack.pop()

            currentTree = parent

        elif i in ['+', '-', '*', '/']:

            currentTree.setRootVal(i)

            currentTree.insertRight('')

            pStack.push(currentTree)

            currentTree = currentTree.getRightChild()

        elif i == ')':

            currentTree = pStack.pop()

        else:

            raise ValueError

    return eTree

pt = buildParseTree("( ( 10 + 5 ) * 3 )")

pt.postorder()  #defined and explained in the next section