Tree traversal - postorder

tree_traversal_postorder_iterative.py

def postorder_traversal_iterating(root):
    if not root:
        return []

    result = []
    stack = [root]
    # get the result in order of node, right, left
    while stack:
        current = stack.pop()
        if current.left:
            stack.append(current.left)
        if current.right:
            stack.append(current.right)
        # visit node
        result.append(current.val)
    # reverse the result to get the target output as left, right node
    return result[::-1]