{"id":"dfs-null-guard-at-callsite","text":"In tree DFS solutions, the inner recursive function is only called on non-None nodes — null checks happen at the call site before recursing into children, not inside the recursive function body.","truth_value":"IN","source":"entries/2026/06/06/sum-of-root-to-leaf-binary-numbers-solution.md","source_url":"","source_hash":"","justifications":[],"dependents":[],"metadata":{},"created_at":"","updated_at":"","reviewed_at":"","verified_at":"","retracted_at":"","explanation":{"steps":[{"node":"dfs-null-guard-at-callsite","truth_value":"IN","reason":"premise"}]}}