javacalculatorpostfix-notation

how to add together the values ​from the RPN algorithm

I’m writing calculator that calculates values ​​from expressions:

3+(23/24)*34/24

I used RPN algorithm: https://en.wikipedia.org/wiki/Reverse_Polish_notation

I have now sorted expression in String:

3 23 24 / 34 * 24 / +

I don't have any idea how can I get value from this expression.

Thx

Solution

  • The basic algorithm is based on a stack-like structure

    For each token in the expression:

    E.g.:

    "3 23 24 / 34 * 24 / +"
                                             Stack
3:  push 3                                   |   3
23: push 23                                  |   3    23
24: push 24                                  |   3    23     24
/:  pop (24),   pop (23),    push 23/24      |   3     0.95
34: push 34                                  |   3     0.95  34
*:  pop (34),   pop (0.95),  push 0.95*34    |   3    32.58
24: push 24                                  |   3    32.58  24
/:  pop (24),   pop (32.58), push 32.58/24   |   3     1.35
+:  pop (1.35), pop (3),     push 3+1.35     |   4.35

    The last value that remains in the stack is the result