下面给出代码
/// <summary>
/// 十机制无符号整数类
/// </summary>
public class DecimalNumber
{
List<byte> _Data;
public List<byte> Data
{
get
{
return _Data;
}
}
public int Length
{
get
{
return _Data.Count;
}
}
public DecimalNumber()
{
_Data = new List<byte>();
}
public DecimalNumber(byte[] data)
{
foreach (byte b in data)
{
System.Diagnostics.Debug.Assert(b >= 0 && b <= 9);
}
_Data = new List<byte>(data);
}
public DecimalNumber(List<byte> data)
{
foreach (byte b in data)
{
System.Diagnostics.Debug.Assert(b >= 0 && b <= 9);
}
_Data = data;
}
/// <summary>
/// 1位10机制数和10进制序列相乘
///
/// </summary>
/// <param name="s">10进制序列</param>
/// <param name="d">1位10机制数</param>
/// <param name="power">10的幂数</param>
/// <returns></returns>
private static List<byte> Multiply(List<byte> s, byte d, int power)
{
System.Diagnostics.Debug.Assert(power >= 0);
System.Diagnostics.Debug.Assert(d >= 0 && d <= 9);
List<byte> result = new List<byte>();
for (int i = 0; i < power; i++)
{
result.Add(0);
}
byte carry = 0; //进位
foreach (byte si in s)
{
System.Diagnostics.Debug.Assert(si >= 0 && si <= 9);
byte r = (byte)(si * d + carry);
byte m = (byte)(r % 10);
carry = (byte)(r / 10);
result.Add(m);
}
if (carry > 0)
{
result.Add(carry);
}
return result;
}
/// <summary>
/// 两个10进制序列相加
/// </summary>
/// <param name="s1">序列1</param>
/// <param name="s2">序列2</param>
/// <returns>相加后的序列</returns>
private static List<byte> Plus(List<byte> s1, List<byte> s2)
{
List<byte> result = new List<byte>();
int c1 = s1.Count;
int c2 = s2.Count;
if (c1 > c2)
{
for (int i = 0; i < c1 - c2; i++)
{
s2.Add(0);
}
}
else if (c1 < c2)
{
for (int i = 0; i < c2 - c1; i++)
{
s1.Add(0);
}
}
byte carry = 0; //进位
for (int i = 0; i < s1.Count; i++)
{
System.Diagnostics.Debug.Assert(s1[i] >= 0 && s1[i] <= 9);
System.Diagnostics.Debug.Assert(s2[i] >= 0 && s2[i] <= 9);
byte r = (byte)(s1[i] + s2[i] + carry);
byte m = (byte)(r % 10);
carry = (byte)(r / 10);
result.Add(m);
}
if (carry > 0)
{
result.Add(carry);
}
return result;
}
public static implicit operator DecimalNumber(string value)
{
List<byte> data = new List<byte>();
for (int i = value.Length - 1; i >= 0; i--)
{
data.Add(byte.Parse(value[i].ToString()));
}
return new DecimalNumber(data);
}
public static implicit operator DecimalNumber(int value)
{
System.Diagnostics.Debug.Assert(value >= 0);
return value.ToString();
}
public static DecimalNumber operator ++(DecimalNumber d)
{
return d + new DecimalNumber(new byte[] { 1 });
}
public static DecimalNumber operator +(DecimalNumber d1, int d2)
{
System.Diagnostics.Debug.Assert(d2 >= 0);
return d1 + d2.ToString();
}
public static DecimalNumber operator +(DecimalNumber d1, DecimalNumber d2)
{
return new DecimalNumber(Plus(d1.Data, d2.Data));
}
public static DecimalNumber operator *(DecimalNumber d1, DecimalNumber d2)
{
List<List<byte>> multiplicationSerial = new List<List<byte>>();
for (int i = 0; i < d1.Data.Count; i++)
{
multiplicationSerial.Add(Multiply(d2.Data, d1.Data[i], i));
}
List<byte> result = new List<byte>();
foreach (List<byte> s in multiplicationSerial)
{
result = Plus(s, result);
}
return new DecimalNumber(result);
}
public override string ToString()
{
StringBuilder str = new StringBuilder();
for (int i = _Data.Count - 1; i >= 0; i--)
{
str.Append(_Data[i].ToString());
}
return str.ToString();
}
}
有了这个类，我们计算阶乘就简单了
下面是计算任意数阶乘的函数
static public DecimalNumber Factorial(int n)
{
if (n < 0)
{
throw new System.ArgumentException("n < 0!");
}
DecimalNumber result = 1;
for (int i = 1; i <= n; i++)
{
result *= i;
}
return result;
}
用这个函数，我们计算0 到 50 的阶乘
for (int i = 0; i <= 50; i++)
{
Console.WriteLine(string.Format("{0}! = {1}", i,
Factorial(i)));
}
2010-02-01 12:46
程序代码：
