{"id":"gcd-strings-commutativity-check","text":"`str1 + str2 == str2 + str1` is both necessary and sufficient for the existence of a common divisor string — this is the key mathematical insight (related to the Fine and Wilf theorem)","truth_value":"IN","source":"entries/2026/06/06/greatest-common-divisor-of-strings-solution.md","source_url":"","source_hash":"","justifications":[],"dependents":[],"metadata":{},"created_at":"","updated_at":"","reviewed_at":"","verified_at":"","retracted_at":"","explanation":{"steps":[{"node":"gcd-strings-commutativity-check","truth_value":"IN","reason":"premise"}]}}