Given the following pushdown automata and input string 00001111, what does the PDA's stack look like once it has gotten through and read the second 1 of the string ...
How many additional edges need to be colored red in order for red edges to make an edge cover of this graph?
Which of the following graphs has an edge covering (as indicated by the red edges)?
Which of the following graphs do not show a vertex cover? (The vertices in the vertex cover are red).
What is the least number of nodes you can have to make a minimum vertex cover of this graph?