C#简单算术运算程序遇到索引越界问题，急！

Question

第一次写C#控制台小程序,用来计算输入如45 + 33形式的算术计算，结果碰到数组下标越界问题，郁闷中...
错误：//分离出第二操作数
    ->这具有错，索引超出了数组界限。 while (char.IsDigit(exp[idx]))
                 digit += exp[idx++];using System;namespace math_op
{
    class math_op_cls
    {
        
      //简单数学计算程序
        static void Main(string[] args)
        {
            Console.WriteLine("请输入一个算术表达式!");
            string exp = Console.ReadLine();
            int idx = 0;
            
            //去掉首部的所有空格
            while (char.IsWhiteSpace(exp[idx]))
                idx++;            //分离出第一个操作数
            //char c;
            string digit = string.Empty;
            //c = exp[idx];
            while (char.IsDigit(exp[idx]))
                 digit += exp[idx++];
                
            //第一个操作书digit1
            int digit1 = Int32.Parse(digit);            //去掉第一操作数和算符中的空格
            while(char.IsDigit(exp[idx]))
                idx++;            //分离出第一个操作符
            char op1 = exp[idx++];            //去掉算符和第二操作数中的空格
            while (char.IsWhiteSpace(exp[idx]))
                idx++;            digit = string.Empty; 
            //分离出第二操作数
            
                
            
                while (char.IsDigit(exp[idx]))
                
                    digit += exp[idx++];
                
            
            //第二个操作数digit2
            int digit2 = Int32.Parse(digit);            float result = 0;
            switch (op1)
            {
                case '+':
                    result = (float)(digit1 + digit2);
                    break;
                case '-':
                    result = (float)(digit1 - digit2);
                    break;
                case '*':
                    result = (float)(digit1 * digit2);
                    break;
                case '/':
                    result = (float)(digit1 / digit2);
                    break;
                case '%':
                    result = (float)(digit1 % digit2);
                    break;
                    
            }            //display result
            Console.WriteLine("结果为:" + result);
             
        }    }
}

Answer 1

这样改下即可:
 while (idx<exp .Length && char.IsDigit(exp[idx]))                digit += exp[idx++];

Answer 2

比如说你输入"24+32"当idx=4时
exp[4]='2';
这时执行digit += exp[idx++];后,digit="32",然后idx++,变成5,再进行下一次循环即:char.IsDigit(exp[5])即超出了范围...所以报错了...

Answer 3

你那样做其实还挺麻烦,给你写了个简单点的:            Console.WriteLine("请输入一个算术表达式!");
            string exp = Console.ReadLine();
            string[] str = exp.Split(new char[] { '+', '-', '*', '/' });
            int digit1 = Convert.ToInt32(str[0]);
            int digit2 = Convert.ToInt32(str[1]);
            char op1 = exp.Substring(str[0].Length, 1)[0];            float result = 0;
            switch (op1)
            {
                case '+':
                    result = (float)(digit1 + digit2);
                    break;
                case '-':
                    result = (float)(digit1 - digit2);
                    break;
                case '*':
                    result = (float)(digit1 * digit2);
                    break;
                case '/':
                    result = (float)(digit1 / digit2);
                    break;
                case '%':
                    result = (float)(digit1 % digit2);
                    break;            }            //display result
            Console.WriteLine("结果为:" + result);

Answer 4

string s = "12 + 34";
            int type=0;
            int i=s.IndexOf('+');
            if (i < 0)
            {
                i = s.IndexOf('-');
                if (i < 0)
                {
                    i = s.IndexOf('*');
                    if (i < 0)
                    {
                        i = s.IndexOf('/');
                        type = 4;
                    }
                    else
                        type = 3;
                }
                else
                    type = 2;
            }
            else
                type = 1;            int num1 = Convert.ToInt32(s.Substring(0, i).Trim());
            int num2 = Convert.ToInt32(s.Substring(i + 1).Trim());
            switch(type)
            {
                case 1:
                    return num1 + num2;
                    break;
                case 2:
                    return num1 - num2;
                    break;
                case 3:
                    return num1 * num2;
                    break;
                case 4:
                    return num1 / num2;
                    break;
                default:
                    break;            }            return 0;

Answer 5

晕，我写的还不支持有空格的情况...再改下..Console.WriteLine("请输入一个算术表达式!");
            string exp = Console.ReadLine();
            string[] str = exp.Split(new char[] { '+', '-', '*', '/','%' });
            int digit1 = Convert.ToInt32(str[0].Trim());
            int digit2 = Convert.ToInt32(str[1].Trim());
            char op1 = exp.Substring(str[0].Length, 1)[0];            float result = 0;
            switch (op1)
            {
                case '+':
                    result = (float)(digit1 + digit2);
                    break;
                case '-':
                    result = (float)(digit1 - digit2);
                    break;
                case '*':
                    result = (float)(digit1 * digit2);
                    break;
                case '/':
                    result = (float)(digit1 / digit2);
                    break;
                case '%':
                    result = (float)(digit1 % digit2);
                    break;            }            //display result
            Console.WriteLine("结果为:" + result);
这样就OK了..