Tree Traversal Pattern

1def inorder_traversal(root):
2    result = []
3    stack = []
4    curr = root
5
6    while curr or stack:
7        # Go left as far as possible
8        while curr:
9            stack.append(curr)
10            curr = curr.left
11
12        # Pop and process
13        curr = stack.pop()
14        result.append(curr.val)
15
16        # Move to right subtree
17        curr = curr.right
18
19    return result