static void Main(string[] args)

{

String a = "5661819829134871879051910331902406583704611050840296586361716685667708181008762236714628309134558913";

String b = "3411153732148254698742623133189372941607630447158281924926002101211802711589274474153788470764953449";

String rst = null;

Console.WriteLine("请输入您要进行的运算：1--加法；2--减法；3--乘法！");

int flag = int.Parse(Console.ReadLine());

if (flag == 1 || flag == 2)

rst = AccountA(a, b, flag);

else if (flag == 3)

rst = AccountB(a, b, flag);

Console.WriteLine("整数A为：");

Console.WriteLine(a);

Console.WriteLine("整数B为：");

Console.WriteLine(b);

Console.WriteLine("运算结果为：");

Console.Write(rst);

Console.ReadKey();

}

static String AccountB(String strA, String strB, int flag)

{

String rst = null;

int[,] a = new int[strB.Length, strA.Length + strB.Length];

int num1, num2, carry = 0, sum = 0, temp;

int[] s = new int[a.GetLength(1)];

for (int i = 0; i < a.GetLength(0); i++)

for (int j = 0; j < a.GetLength(1); j++)

a[i, j] = 0;

for (int i = strB.Length - 1; i >= 0; i--)

{

int j = strA.Length - 1;

for (; j >= 0; j--)

{

num1 = int.Parse(strA[j].ToString());

num2 = int.Parse(strB[i].ToString());

temp = num1 * num2 + carry;

a[strB.Length - i - 1, i + j + 1] = temp % 10;

carry = temp / 10;

}

a[strB.Length - i - 1, i + j + 1] = carry;

carry = 0;

}

for (int i = a.GetLength(1) - 1; i > 0; i--)

{

temp = 0;

for (int j = 0; j < a.GetLength(0); j++)

temp += a[j, i];

temp += carry;

s[i] = temp % 10;

carry = temp / 10;

}

s[0] = carry + a[a.GetLength(0) - 1, 0];

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

rst += s[i].ToString();

//Code End

return rst;

}

static String AccountA(String strA, String strB, int flag)

{

String rst = null;

String strC = null, strD = null;

char[] a = new char[strA.Length + 1];

int b, c, carry = 0, borrow = 0, temp = 0;

//Code Begin

if (flag == 1)

{

for (int i = strA.Length - 1; i >= 0; i--)

{

b = int.Parse(strA[i].ToString());

c = int.Parse(strB[i].ToString());

temp = b + c + carry;

a[i + 1] = (char)(temp % 10 + 48);

carry = temp / 10;

}

a[0] = (char)(carry + 48);

if (a[0] != '0')

rst += a[0];

else

rst = null;

for (int i = 1; i < a.Length; i++)

rst += a[i];

}

else

{

if (strA.CompareTo(strB) < 0)

{

strC = strB;

strD = strA;

rst += '-';

}

else

{

strC = strA;

strD = strB;

}

for (int i = strC.Length - 1; i >= 0; i--)

{

b = int.Parse(strC[i].ToString());

c = int.Parse(strD[i].ToString());

temp = b - c - borrow;

a[i + 1] = (char)((temp + 10) % 10 + 48);

if (temp < 0)

borrow = 1;

else

borrow = 0;

}

for (int i = 1; i < a.Length; )

if (a[i] == '0' && (rst == '-'.ToString() || rst == null))

i++;

else

{

rst += a[i];

i++;

}

}

return rst;

}

}