Hoodies at coding blocks, tle

#1

I did Hoodies at coding blocks using a stack, it is taking o(n) time for both insertion and deletion and o(n) space too. Here is my solution, using linked list would have made the D o(1) but query E will still take O(n). so what should be the optimized way to do this question, I couldn’t think of any way of doing it with the queue?

#2

Don’t use stack in this question use queue and see that queue is fifo or lilo last in last out and stack is lifo

#3

Make a boolean function is same course than only use queue