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RPN Problems (Order of Operations) [closed]

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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.

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