$3.$ Write an algorithm Replace that takes a stack and two items. If the first item is in the stack, replace it with the second item, leaving the rest of the stack unchanged.

Replace$($stack$,$ item$1,$ item$2)$

Pop$($stack$,$ item$)$

WHILE$($Item $!=$ item$1)$

Push$($newStack$,$ item$1)$

Pop$($stack$,$ item$)$

If$($NOT Empty$($Stack$))$

Push$($newStack$,$ item$2)$

WHILE$($NOT Empty$($newStack$))$

Pop$($newStack$,$ item$)$

Push$($stack$,$ item$)$