Exercise-Reverse Polish Notation (RPN)

a) 2+3+4
=> 34+
=> 234++

b) (2+3)*4
=> 23+
=> 423+*

c) 2*(5+2*3)
=> 23*
=> 23*5+
=> 223*5+*

d) (3+4)*(20-(3*4+2))
=> 34*
=> 34*2+
=> 2034*2+-
=> 34+2034*2+-*

e) 5*(3+4)-(2*(2+2*(1+2)))
=> 12+
=> 212+*
=> 2212+*+
=> 22212+*+*
=> 34+22212+*+*-
=> 534+*22212+*+*-