Function evaluate

ParseTree.py:38–48

(parseTree)

# 递归实现两个叶结点的运算
def evaluate(parseTree):
    opers = {'+':operator.add, '-':operator.sub, '*':operator.mul, '/':operator.truediv}

    leftC = parseTree.getLeftChild()
    rightC = parseTree.getRightChild()

    if leftC and rightC:
        fn = opers[parseTree.getRootVal()]
        return fn(evaluate(leftC), evaluate(rightC))
    else:
        return parseTree.getRootVal()

# 递归实现树的后序遍历
def postorder(tree):