Identifying the stateless preorder traversal pattern

The stateless preorder traversal can solve most binary tree problems where data needs to be passed down from parent nodes to child nodes for processing. These are generally easy or medium problems where we need to process every node using the aggregated value of some function f over all the nodes in the path from the root node to itself. The stateless implementation can only solve problems where no state (common) information is shared between all nodes, and each node has access to only its copy of local variables.

If the problem statement or its solution follows the generic template below, it can be solved by applying the stateless preorder traversal technique.