题解 | #高精度整数加法#

using System;
using System.Linq;
using System.Text;

namespace HJ57
{
    internal class Program
    {
        static void Main(string[] args)
        {
            var str01 = Console.ReadLine();
            var str02 = Console.ReadLine();
            if (str01.Length < str02.Length)
            {
                str01 = str01.PadLeft(str02.Length, '0');
            }
            else
            {
                str02 = str02.PadLeft(str01.Length, '0');
            }

            byte[] bytes = new byte[str01.Length + 1];
            //低位在后，从低位加起
            for (int i = str01.Length - 1; i >= 0; i--)
            {
                byte b1 = Convert.ToByte(str01[i].ToString());
                byte b2 = Convert.ToByte(str02[i].ToString());
                byte sum = (byte)(bytes[i + 1] + b1 + b2);
                if (sum >= 10)
                {
                    bytes[i + 1] = (byte)(sum - 10);
                    bytes[i] = 1;
                }
                else
                {
                    bytes[i + 1] = sum;
                }
            }

            StringBuilder sb = new StringBuilder();
            for (int i = 0; i < bytes.Length; i++)
            {
                sb.Append(Convert.ToString(bytes[i]));
            }
            if (sb[0] == '0')
            {
                sb.Remove(0,1);
            }
            Console.WriteLine(sb.ToString());
        }
    }
}