我正在学习 PDA，并且我知道如何为给定的绘制 PDA 跟踪一组符号或字母表。但是，我不知道如何跟踪给定的 PDA（以书面形式）见下文。
所以这是一个书面的PDA：
Q={s0,f}
Σ={a,b,c}
Γ={S,X,a,b,c}
F={f}
δ={((s0,ε,ε),(f,S)),
((f,ε,S)(f,aSc)),
((f,ε,S)(f,X)),
((f,ε,X)(f,bXc)),
((f,ε,X)(f,ε)),
((f,a,a)(f,ε)),
((f,b,b)(f,ε)),
((f,c,c)(f,ε))
}
问题问：
Trace one possible computational path of your pushdown automaton from with
the input abccc. This string will not be accepted. Explain how you know that your computation has not accepted the input, that is, why the state and stack configuration after the input has been used up is not an accepting one.
答案是：
State Stack
s0 ε
f S
f aSc
f Sc
f Xc
f bXcc
f Xcc
f cc
f c
f ε
我不明白堆栈符号。我想如果ε在堆栈的末尾有一个输入被接受：S？
如果有人可以向我解释，我将不胜感激
谢谢