{"id":"island-perimeter-boundary-guard","text":"The `r > 0` and `c > 0` guards are the only bounds checks needed because the algorithm only examines up and left neighbors, never down or right.","truth_value":"IN","source":"entries/2026/06/06/island-perimeter-solution.md","source_url":"","source_hash":"","justifications":[],"dependents":[],"metadata":{},"created_at":"","updated_at":"","reviewed_at":"","verified_at":"","retracted_at":"","explanation":{"steps":[{"node":"island-perimeter-boundary-guard","truth_value":"IN","reason":"premise"}]}}