Pushdown automata may contain transitions that are never used in any accepting run of the automaton. We present an algorithm for detecting such useless transitions. A finite automaton that captures the possible stack content during runs of the pushdown automaton, is first constructed in a forward procedure to determine which transitions are reachable, and then employed in a backward procedure to determine which of these transitions can lead to a final state. An implementation of the algorithm is shown to exhibit a favorable performance.

中文翻译：

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检测下推自动机中的无用转换

下推自动机可能包含在自动机的任何接受运行中从未使用过的转换。我们提出了一种检测这种无用转换的算法。在下推自动机运行期间捕获可能的堆栈内容的有限自动机首先在前向过程中构建以确定哪些转换是可达的，然后在后向过程中使用以确定这些转换中的哪些可以导致最终状态。该算法的实现显示出良好的性能。