Understanding the stateless postorder traversal pattern

The postorder traversal follows the left-right-node processing sequence, where a node is processed after processing both its left and right subtrees recursively. Because a node is processed after its left and right subtrees, the postorder traversal is ideal for solving problems where data must be processed and passed up from child nodes to the parent node. This makes postorder traversal the ideal solution for solving binary tree problems that require a bottom-up processing. Every node processes values passed from its children and passes the result to its parent.

There are two ways to pass data between nodes. One requires maintaining some shared state, while the other is completely stateless. The choice between these options depends on the problem. The stateless postorder traversal is the regular postorder traversal technique that passes data from child nodes to the parent node instead of sharing a single copy between nodes.