{"id":"postorder-accumulator-pattern","text":"Tree problems in this repo use a recurring idiom: a postorder DFS function returns one value (e.g., subtree sum, height) while accumulating a second aggregate (e.g., tilt, diameter) into a `nonlocal` closure variable.","truth_value":"IN","source":"entries/2026/06/06/binary-tree-tilt-solution.md","source_url":"","source_hash":"","justifications":[],"dependents":["tree-postorder-closure-idiom"],"metadata":{},"created_at":"","updated_at":"","reviewed_at":"","verified_at":"","retracted_at":"","explanation":{"steps":[{"node":"postorder-accumulator-pattern","truth_value":"IN","reason":"premise"}]}}