求用1，2，5这三个数不同个数组合的和为100的组合个数

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

namespace ExchangeDemo
{
class Program
{
static void Main(string[] args)
{
int number1, number2;
Console.WriteLine("求用1，2，5这三个数不同个数组合的和为100的组合个数");
number1 = SimpleSolution();
Console.WriteLine("算法一组合数：" + number1 + "");
number2 = Optimize();
Console.WriteLine("算法二组合数：" + number2 + "\r\n");

int nu1 = 0;
int nu2 = 0;
int nu5 = 0;
int count = 0;
for (nu5 = 0; nu5 < 21; nu5++)
{
for (nu2 = 0; nu2 < 51; nu2++)
{
for (nu1 = 0; nu1 < 101; nu1++)
{
if (nu1 + nu2*2 + nu5*5 == 100)
{
if (nu1 != 0)
{
Console.Write("" + nu1 + "*1");
}
if (nu2 != 0 && nu5 != 0)
{
Console.Write("+" + nu2 + "*2+" + nu5 + "*5");
}
else if (nu2 != 0 && nu5 == 0)
{
Console.Write("+" + nu2 + "*2");
}
else if (nu2 == 0 && nu5 != 0)
{
Console.Write("+" + nu5 + "*5");
}
Console.WriteLine("=100\r\n");
count++;
}
}
}
}
Console.WriteLine("总的组合数为" + count + "");
Console.Read();

}
public static int SimpleSolution()
{
int number=0;
for(int i=0;i<=100;i++)
for(int j=0;j<=50;j++)
for(int k=0;k<=20;k++)
{
if(i+2*j+5*k==100)
number++;
}
return number;
}

public static int Optimize()
{
//组合总数为100以内的偶数+95以内的奇数+90以内的偶数+...+5以内的奇数+1
int number = 0;
for (int m = 0; m <= 100; m += 5)
{
number += (m + 2) / 2;
// 某个偶数m以内的偶数个数（包括0）可以表示为m/2+1=(m+2)/2
//某个奇数m以内的奇数个数也可以表示为(m+2)/2
}
return number;
}
}
}