A stack is a LIFO $($last in$,$ first out$)$ structure. For example, if we have a stack of integers with the following value:

TOP $($last value added to the stack$)$

$3$

$2$

$1$

And if the value $4$ was the most recently added value to the stack, then it is the top of the stack.

One way to implement the concept of a stack is with a vector object $--$ we can implement a templated stack class with a vector as the underlying implementation of this. stack.

One of the functions in this templated stack class is a top$()$ function, which returns the top of the stack. Which function in the underlying vector object should be called in the body of the top$()$ function?

front$()$

pop$\_$front$()$

back$()$