tree traversal without recursion

treeTraversal.py

"""
class Node:
    def __init__(self, data=None, left=None, right=None):
        self.data = data
        self.left = left
        self.right = right
"""

def preOrder(root):
    pass

def postOrder(root):
    stack = []
    curr = root
    while curr :
        stack.append(curr)
        if curr.right:
            stack.append(curr.right)
        if curr.left:
            stack.append(curr.left)
    stack.reverse()
    print(' '.join(map, stack))

def inOrder(root):
    stack = []
    res = []
    curr = root
    while curr or stack :
        if not curr :
            tmp = stack.pop()
            res.append(tmp.data)
            curr = tmp.right
            continue
        stack.append(curr)
        curr = curr.left
    print(' '.join(map(str, res)))

# 按层遍历
def levelOrder(root):
    queue = [root]
    res = []
    while queue:
        curr = queue.pop(0)
        res.append(curr.data)
        if curr.left:
            queue.append(curr.left)
        if curr.right:
            queue.append(curr.right)
    print(' '.join(map(str, res)))