Help me understand Inorder Traversal without using recursion

Question

I am able to understand preorder traversal without using recursion, but I\'m having a hard time with inorder traversal. I just don\'t seem to get it, perhaps, because I have

Answer 1

@Victor, I have some suggestion on your implementation trying to push the state into the stack. I don't see it is necessary. Because every element you take from the stack is already left traversed. so instead of store the information into the stack, all we need is a flag to indicate if the next node to be processed is from that stack or not. Following is my implementation which works fine:

def intraverse(node):
    stack = []
    leftChecked = False
    while node != None:
        if not leftChecked and node.left != None:
            stack.append(node)
            node = node.left
        else:
            print node.data
            if node.right != None:
                node = node.right
                leftChecked = False
            elif len(stack)>0:
                node = stack.pop()
                leftChecked = True
            else:
                node = None