例如100000000*100000000两个一亿相乘的算法~~~~~~~~

这样算有意思吗？晕~~~~
int的定义域没那么大，2个那么大的数相乘只是会出现错误，除非定义为double类型。才不会出现错误

就我现在的水平来说...不可能...

以前写过的，我找找看

在这里头：http://hi.baidu.com/visolleon/blog/item/8d2fc8af9d7507cf7cd92aa2.html

程序语言中整数类型的大小都是有限的，在C#中int(System.Int32)的取值范围为：-2,147,483,648 到 2,147,483,647；但如果实际运用中，有一个数大于2,147,483,647或者小于-2,147,483,648，那就可能出错，导致无法运算，下面的程序运用乘法的运算方法，用位数字的叠加来组合形成正确的结果，程序如下（此程序未考虑负数）：

using System;
using System.Collections.Generic;
using System.Text;

namespace BigNumber
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.Write("Number A is : ");
            string Aa = Console.ReadLine();
            int[] A = new int[Aa.Length];
            for (int i = 0; i < Aa.Length; i++)
            {
                A[Aa.Length-1-i] = Convert.ToInt32(Aa.Substring(i, 1));
                //Console.WriteLine(A[Aa.Length - 1 - i]);
            }

            Console.Write("Number B is : ");
            string Bb = Console.ReadLine();
            int[] B = new int[Bb.Length];
            for (int i = 0; i < Bb.Length; i++)
            {
                B[Bb.Length-1-i] = Convert.ToInt32(Bb.Substring(i, 1));
                //Console.WriteLine(B[Bb.Length - 1 - i]);
            }
            int[,] sum = new int[Aa.Length,Bb.Length];
            int[] wsum = new int[Aa.Length + Bb.Length];
            for (int i = 0; i < Aa.Length; i++)
            {
                for (int j = 0; j < Bb.Length; j++)
                {
                    sum[i,j] = A[i]*B[j];
                    wsum[i + j] = wsum[i + j] + sum[i, j];
                    if (wsum[i + j].ToString().Length > 1)
                    {
                        wsum[i + j + 1] = wsum[i + j + 1] + wsum[i + j]/10;
                        wsum[i + j] = Convert.ToInt32(wsum[i + j].ToString().Substring(1, 1));
                    }
                    Console.WriteLine("sum[" + i + "," + j + "] = {0}", sum[i, j]);
                }
            }
            string end = "";
            for (int m = 0; m < Aa.Length + Bb.Length; m++)
            {
                Console.WriteLine("wsum[" + m + "] = {0}", wsum[m]);
                end = wsum[m].ToString() + end;
            }
            Console.WriteLine();
            Console.WriteLine("================================================================");
            Console.WriteLine("计算结果为：{0}",end);
            Console.ReadLine();
        }
    }
}

嗯，我以前学汇编的时候也是用多字节位数叠加实现的无限长度四则运算的，和上面的方法类似