Question about A3(DeadCodeDetection)

[RacerZ-fighting]

When doing graph traversal, I first chose a LinkedList to maintain all visited nodes.
But I can't figure out why there would be a false negative test case.

        List<Stmt> isVisited = new LinkedList<>();
        ArrayDeque<Stmt> queue = new ArrayDeque<>();    // BFS queue
        queue.add(cfg.getEntry());

Then, if I change to use a HashSet, all test cases will pass.