{"id":"parent-context-threading-via-parameter","text":"`sum_of_left_leaves` passes an `is_left` boolean down the recursion so each node knows its relationship to its parent, rather than using the parent-look-ahead pattern where the parent checks `node.left.left is None`.","truth_value":"IN","source":"entries/2026/06/06/sum-of-left-leaves-solution.md","source_url":"","source_hash":"","justifications":[],"dependents":[],"metadata":{},"created_at":"","updated_at":"","reviewed_at":"","verified_at":"","retracted_at":"","explanation":{"steps":[{"node":"parent-context-threading-via-parameter","truth_value":"IN","reason":"premise"}]}}