函数提高代码的重用性，是一段封闭的代码。
自己练习做了几个函数
/// <summary>
/// 输入一个数，求和函数
/// </summary>
/// <param name="n"></param>
/// <returns></returns>
public int qiuhe(int n)
{
int sum = 0;
for (int i = 0; i <=n; i++)
{
sum += i;
}
return sum;
}
/// <summary>
/// 几千几百减几百不退位，无返回值，无参数
/// </summary>
public void butuiwei()
{
Random r = new Random();
int c, d, e, f;
int a = r.Next(1, 10);
int b = r.Next(1, 10);
f = r.Next(1, b);
d = a * 1000 + b * 100;
e = f * 100;
if (b >= f)
{
c = d - e;
Console.WriteLine(d + "-" + e + "=" + c);
}
else
{
Console.WriteLine("错误");
}
}
/// <summary>
/// 判断闰年，返回结果
/// </summary>
/// <param name="s"></param>
/// <returns></returns>
public string runnian(string s)
{
string s1 = "";
string s2;
try
{
DateTime rn1 = Convert.ToDateTime(s + "-2-29");
s1 = "年是闰年";
}
catch (Exception)
{
s1 = "年不是闰年";
}
finally
{
s2 = s + s1;
}
return s2;
}
/// <summary>
/// 给出单词，打印单词的各个字母
/// </summary>
/// <param name="s"></param>
public void danci(string s)
{
int a = s.Length;
for (int i = 0; i < a; i++)
{
Console.WriteLine(s.Substring(i, 1));
}
}
/// <summary>
/// 冒泡排序，由大到小
/// </summary>
/// <param name="a">int 数组a</param>
public int[] paixu(int[] a)
{
for (int i = 0; i < a.Length; i++)
{
for (int j = i; j < a.Length - 1; j++)
{
if (a[i] < a[j + 1])
{
int b;
b = a[i];
a[i] = a[j + 1];
a[j + 1] = b;
}
}
}
return a;
}
/// <summary>
/// 数组求和
/// </summary>
/// <param name="a"></param>
/// <returns></returns>
public int shuzuqiuhe(int[] a)
{
int x = 0;
for (int i = 0; i < a.Length; i++)
{
x = a[i] + x;
}
return x;
}