Queues size always equals to number of vertices.
Hence queue size is always in this question = # of vertices 7 ( min Or max case ) .
Max size of stack :- means no pop operation will occurs in dfs ( stack) .. Hence here we start vertices A .
Sequence is A B C D G E F max size of stack is 7 .
Min size of stack :- means choose a path where more number of operation done.
Sequence for minimum :- F E C D G B A HERE after C , path c d g push in stack and after delet g and d from stack . Now we at point C, and now onwards we add b and a in stack..... Hence total minimum size is 5 .