Expressions

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Algo
{
    class Program
    {
        static int Evaluate2(string expr)
        {
            Stack<char> op = new Stack<char>();
            Stack<int> nums = new Stack<int>();

            foreach (var ch in expr)
            {
                if (ch == '+' || ch == '*')
                {
                    op.Push(ch);
                }
                else if (ch >= '0' && ch <= '9')
                {
                    nums.Push(ch - '0');
                }
                else if (ch == '(')
                {
                    nums.Push('(');
                }
                else if (ch == ')')
                {
                    int result = 0;
                    if (op.Peek() == '+')
                    {
                        while (nums.Peek() != '(')
                        {
                            result += nums.Peek();
                            nums.Pop();
                        }
                    }
                    else if (op.Peek() == '*')
                    {
                        result = 1;
                        while (nums.Peek() != '(')
                        {
                            result *= nums.Peek();
                            nums.Pop();
                        }
                    }
                    nums.Pop(); // remove (
                    nums.Push(result);
                    op.Pop();
                }
            }
            return nums.Peek();
        }

        static int Evaluate1(string expr)
        {
            Stack<char> op = new Stack<char>();
            Stack<int> nums = new Stack<int>();

            foreach (var ch in expr)
            {
                if (ch == '+' || ch == '*')
                {
                    op.Push(ch);
                }
                else if (ch >= '0' && ch <= '9')
                {
                    nums.Push(ch - '0');
                }
                else if (ch == ')')
                {
                    char oper = op.Pop();
                    int result = 0;
                    if (oper == '+')
                    {
                        result = nums.Pop() + nums.Pop();
                    }
                    else if (oper == '*')
                    {
                        result = nums.Pop() * nums.Pop();
                    }
                    nums.Push(result);
                }
            }
            return nums.Peek();
        }

        static void Main(string[] args)
        {
            Console.WriteLine(Evaluate1("+(2,*(3,8))"));
        }
    }
}