{"id":"non-alpha-positional-invariant","text":"In the Reverse Only Letters solution, non-alphabetic characters are guaranteed to remain at their original indices — the two-pointer loop only swaps when both pointers point at `isalpha()` characters.","truth_value":"IN","source":"entries/2026/06/06/reverse-only-letters-solution.md","source_url":"","source_hash":"","justifications":[],"dependents":[],"metadata":{},"created_at":"","updated_at":"","reviewed_at":"","verified_at":"","retracted_at":"","explanation":{"steps":[{"node":"non-alpha-positional-invariant","truth_value":"IN","reason":"premise"}]}}