{"id":"stack-queue-deque-as-fifo","text":"deque is used strictly as a FIFO queue (only append, popleft, len, and [0] indexing); no deque-specific operations like appendleft are used.","truth_value":"IN","source":"entries/2026/06/06/implement-stack-using-queues-solution.md","source_url":"","source_hash":"","justifications":[],"dependents":[],"metadata":{},"created_at":"","updated_at":"","reviewed_at":"","verified_at":"","retracted_at":"","explanation":{"steps":[{"node":"stack-queue-deque-as-fifo","truth_value":"IN","reason":"premise"}]}}