RPN Problems (Order of Operations) [closed]

This question is unlikely to help any future visitors; it is only relevant to a small geographic area, a specific moment in time, or an extraordinarily narrow situation that is not generally applicable to the worldwide audience of the internet. For help making this question more broadly applicable, visit the help center. Closed 11 years ago.

I'm trying to make a simple calculator with order of operations. I had read in the Internet and found the algorithm of RPN (Reverse Polish notation).

EDIT:

Lets take an example: 2 * 5 - 3 + 4

Ok, I did as you both said check it out now开发者_运维问答:

Proc is string array of both numbers and operations. Proc will be {2, *, 5, -, 3, +, 4}

This is the code:

    int tempt = 0;
    Stack <Double> stc = new Stack <Double>();
    while (tempt < proc.length)
    {
        try
        {
            Double num = Double.parseDouble(proc[tempt]);
            stc.push(num);
            tempt++;
        }
        catch (Exception e)
        {
            char [] stcs = proc[tempt].toCharArray();
            switch (stcs[0])
            {
            case '+':
            {
                double a2 = stc.pop();
                double a1 = stc.pop();
                stc.push(a1 + a2);
                tempt++;
                break;
            }
            case '-':
            {
                double a2 = stc.pop();
                double a1 = stc.pop();
                stc.push(a1 - a2);
                tempt++;
                break;
            }
            case 'x':
            {
                double a2 = stc.pop();
                double a1 = stc.pop();
                stc.push(a1 * a2);
                tempt++;
                break;
            }
            case '÷':
            {
                double a2 = stc.pop();
                double a1 = stc.pop();
                stc.push(a1 / a2);
                tempt++;
                break;
            }
        }

        }

STILL DOESNT WORK

How can I make it work as well? HELP ME PLS!

---

You've got the algorithm wrong. 2 * 5 - 3 + 4 in RPN translates to: 2 5 * 3 - 4 +. I don't know why you are treating numbers and symbols independently in two separate lists: in Reverse Polish notation:

2 3 + 4 * === (2 + 3) * 4

while

2 3 4 + * === 2 * (3 + 4)

That being said your program is almost correct except that for input you should take a series of symbols (both values and operators). Now you read symbols from left to right. If it is a number, push it onto the stack. If operator: pop top two values and push the result. That's it!

---

UPDATE: Example

Input: 2 5 * 3 - 4 +

Stack: []

Iteration I: (reading 2 from input)

Input: 5 * 3 - 4 +

Stack: [2]

Iteration II: (reading 5 from input)

Input: * 3 - 4 +

Stack: [2, 5]

Iteration III: (reading * from input)

Input: 3 - 4 +

Stack: [2 * 5] == [10]

Iteration IV: (reading 3 from input)

Input: - 4 +

Stack: [10, 3]

Iteration V: (reading - from input)

Input: 4 +

Stack: [10 - 3] == [7]

Iteration VI: (reading 4 from input)

Input: +

Stack: [7, 4]

Iteration VII: (reading + from input)

Input: ``

Stack: [7 + 4] == [11]

Result: 11 (no further input, one and only element on the stack is the result)

---

UPDATE 2: C'mon!

You are writing a program to interpret RPN but you are feeding it with infix notation! Try with this input:

String[] proc = new String[]{"2", "5", "x", "3", "-", "4", "+"};

There are several other flaws in your code (duplication, exception driven flow control, no error handling), but essentially with this input it should work.