{"id":"sentinel-defaults-safe-under-constraints","text":"Sentinel initial values (-1, 0, None) never collide with valid data because LeetCode's input constraints guarantee the sentinel falls outside the problem's value domain, making sentinel-based boundary elimination unconditionally safe within the stated contract.","truth_value":"IN","source":"","source_url":"","source_hash":"","justifications":[{"type":"SL","antecedents":["sentinel-initialization-encodes-boundary-conditions","no-validation-is-deliberate-contract"],"outlist":["rook-position-default-zero"],"label":"Sentinel safety depends on constraints excluding the sentinel value from valid inputs — rook defaulting to (0,0) shows this breaks when the sentinel IS a valid position"}],"dependents":["streaming-boundary-handling-robust-in-practice"],"metadata":{"last_reviewed":"2026-06-07T22:02:22","review_result":"invalid"},"created_at":"","updated_at":"","reviewed_at":"","verified_at":"","retracted_at":"","explanation":{"steps":[{"node":"sentinel-defaults-safe-under-constraints","truth_value":"IN","reason":"SL justification valid","antecedents":["sentinel-initialization-encodes-boundary-conditions","no-validation-is-deliberate-contract"],"label":"Sentinel safety depends on constraints excluding the sentinel value from valid inputs — rook defaulting to (0,0) shows this breaks when the sentinel IS a valid position","outlist":["rook-position-default-zero"]},{"node":"sentinel-initialization-encodes-boundary-conditions","truth_value":"IN","reason":"SL justification valid","antecedents":["ascending-check-uses-sentinel-minus-one","k-length-apart-sentinel-minus-one","prev-zero-sentinel","getheight-sentinel-neg1"],"label":"all four use domain-specific sentinels (-1 for \"no previous index\", 0 for \"no previous group\", -1 for \"any subtree unbalanced\") that make the first loop iteration produce the correct vacuous result without an explicit guard"},{"node":"ascending-check-uses-sentinel-minus-one","truth_value":"IN","reason":"premise"},{"node":"k-length-apart-sentinel-minus-one","truth_value":"IN","reason":"premise"},{"node":"prev-zero-sentinel","truth_value":"IN","reason":"premise"},{"node":"getheight-sentinel-neg1","truth_value":"IN","reason":"premise"},{"node":"no-validation-is-deliberate-contract","truth_value":"IN","reason":"SL justification valid","antecedents":["solutions-no-input-validation","no-input-validation-convention","solutions-trust-leetcode-preconditions","leetcode-solutions-no-validation-convention"],"label":"Validation omission is a consistent design decision, not accumulated technical debt"},{"node":"solutions-no-input-validation","truth_value":"IN","reason":"premise"},{"node":"no-input-validation-convention","truth_value":"IN","reason":"premise"},{"node":"solutions-trust-leetcode-preconditions","truth_value":"IN","reason":"premise"},{"node":"leetcode-solutions-no-validation-convention","truth_value":"IN","reason":"premise"}]}}