def ParseTree(exp):
    exp = exp.split()
    expTree = BinaryTree('')  # create an empty tree
    parents = Stack()  # create stack to hold the parents
    parents.push(expTree)  # root is kept on bttm of stack

    for item in exp:

        if item == '(':  # next item will be var or int, followed by an operator - we need to move down
            expTree.insertLeft(
                ''
            )  # insert empty node on left which will be a num or int later
            parents.push(expTree)
            expTree = expTree.getLeftChild(
            )  # move down so num or var can be placed

        elif item == ')':
            expTree = parents.pop()

        elif item in OPERATORS:
            expTree.key = item  # operator is placed at current node
            expTree.insertRight('')
            parents.push(expTree)
            expTree = expTree.getRightChild(
            )  # we move right because a symbol or an num must be placed next

        elif item not in SYMBOLS and item not in OPERATORS and item != "(" and item != ")":
            expTree.key = float(
                item
            )  # entering them as float in case anyone inputs float values
            expTree = parents.pop()

        elif item in SYMBOLS:
            expTree.key = item
            expTree = parents.pop()

    return expTree
# _*_ coding: utf-8 -*-
# @Time      : 8/27/20 3:19 PM
# @Author    : title_z
# @Filename  : Binarytree.py

from pythonds.trees import BinaryTree

# r = BinaryTree(3)
# BinaryTree.insertLeft(r, 4)
# BinaryTree.insertLeft(r, 5)
# BinaryTree.insertRight(r, 6)
# BinaryTree.insertRight(r, 7)
# l = BinaryTree.getLeftChild(r)
# print(l)

r = BinaryTree('a')
r.insertLeft('b')
r.insertRight('c')
r.getRightChild().setRootVal('hello')
r.getLeftChild().insertRight('d')
print(r)
# 3. Using the findSuccesor method, write a non-recursive inorder traversal for a binary search tree.
from pythonds.basic import Stack
from pythonds.trees import BinaryTree

# Inorder traversal using a Stack


def inorderTrav(tree):
    posStack = Stack()
    current = tree

    while current != None or posStack.size() > 0:
        # Left-most node
        while (current != None):
            posStack.push(current)
            current = current.getLeftChild()
        current = posStack.pop()
        print(current.getRootVal())

        current = current.getRightChild()


tree = BinaryTree("A")
tree.insertLeft("B")
tree.getLeftChild().insertLeft("C")
tree.getLeftChild().insertRight("D")
tree.insertRight("E")
inorderTrav(tree)
Esempio n. 4
0
        else:
            return tree.getRootVal()


# 还原完全括号表达式
def printExp(tree):
    sumVal = ''

    if tree:
        currentVal = tree.getRootVal()
        if isinstance(currentVal, int):
            sumVal = printExp(tree.getLeftChild())
        else:
            sumVal = '(' + printExp(tree.getLeftChild())

        sumVal = sumVal + str(tree.getRootVal())

        if isinstance(currentVal, int):
            sumVal = sumVal + printExp(tree.getRightChild())
        else:
            sumVal = sumVal + printExp(tree.getRightChild()) + ')'
    return sumVal


etree = BinaryTree('*')
etree.insertRight(2)
etree.insertLeft(3)
preorder(etree)
print(printExp(etree))
print(postorderEval(etree))