using System;

using System.Collections.Generic;

using System.Text;

​

    // http://www.programcreek.com/2012/12/leetcode-evaluate-reverse-polish-notation/

public class Sample {

   public static void Main(string[] args){

        String str = "5+((5+2)*4)-3";

        String result=LengyelFormaKonvertalas(str);

        Console.WriteLine(evalRPN(result));

        Console.ReadLine();

    }

​

    static String LengyelFormaKonvertalas(String input){

       Stack<char> stack = new Stack<char>();

       String str = input.Replace(" ", string.Empty);

       StringBuilder formula = new StringBuilder();

       for (int i = 0; i < str.Length; i++){

           char x=str[i];

           if (x == '(')

               stack.Push(x);

           else if (x == ')'){

               while(stack.Count>0 && stack.Peek() != '(')

                   formula.Append(stack.Pop());

               stack.Pop();

           } else if (IsOperandus(x)){

               formula.Append(x);

           } else if (IsOperator(x)) {

               while(stack.Count>0 && stack.Peek() != '(' && Prior(x)<=Prior(stack.Peek()) )

                   formula.Append(stack.Pop());

               stack.Push(x);

           }

           else {

              char y= stack.Pop();

              if (y!='(') 

                  formula.Append(y);

           }

       }

       while (stack.Count>0) {

           formula.Append(stack.Pop());

       }

       return formula.ToString();

    }

​

    static bool IsOperator(char c){

        return (c=='-'|| c=='+' || c=='*' || c=='/');

    }

    static bool IsOperandus(char c){

        return (c>='0' && c<='9' || c=='.');

    }

    static int Prior(char c){

        switch (c){

            case '=':

                return 1;

            case '+':

                return 2;

            case '-':

                return 2;

            case '*':

                return 3;

            case '/':

                return 3;

            case '^':

                return 4;

            default:

                throw new ArgumentException("Rossz parameter");                                          

        }

    }

    private static int evalRPN(

        string tokens

        )

    {

        if (tokens == null || tokens.Length < 3) return 0;

        var stack = new Stack<int>();   

        var operations = "+-*/";

        for (var i = 0; i<tokens.Length; i++){

            if (!operations.Contains(tokens[i].ToString())) {

                stack.Push(Int32.Parse(tokens[i].ToString()));

            } else {

                var b = stack.Pop();

                var a = stack.Pop();

                switch (tokens[i]) {

                    case '+':

                        stack.Push(a+b);

                        break;

                    case '-':

                        stack.Push(a-b);

                        break;

                    case '*':

                        stack.Push(a*b);

                        break;

                    case '/':

                        stack.Push(a/b);

                        break;

                }

            }

        }

        return stack.Pop();

    }

}