求N的阶乘的方法 :
public static Fab(int n)
{
if(n==1) return 1;
return n * Fab(n-1);
}
问:1000的阶乘未尾有几个0?
解: 要产生0,那么分解后的最小因子一定要有2和5,而2个数一定会多于5,那么只需要求出5的个数就可以了。
那么结果 :1000/5=200,200/5=40,40/5=8,(int)8/5=1
共有200+40+8+1=249个0。
输出所有水仙花数
一个N(N>=3)位数,其值 等于每位N次方之和
1
for (int i = 100; i <= 999; i++)
2
{
3![](/Images/OutliningIndicators/InBlock.gif)
4
if (Math.Pow(i / 100, 3) +
5
Math.Pow((i / 10) - (i / 100) * 10, 3) +
6
Math.Pow(i - i / 10 * 10, 3) == i)
7
{
8
System.Console.WriteLine(
9
"{0}:[{1}|{2}|{3}]", i, i / 100, (i / 10) - (i / 100) * 10, i - i / 10 * 10);
10
}
11
}
![](/Images/OutliningIndicators/None.gif)
2
![](/Images/OutliningIndicators/ExpandedBlockStart.gif)
3
![](/Images/OutliningIndicators/InBlock.gif)
4
![](/Images/OutliningIndicators/InBlock.gif)
5
![](/Images/OutliningIndicators/InBlock.gif)
6
![](/Images/OutliningIndicators/InBlock.gif)
7
![](/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
8
![](/Images/OutliningIndicators/InBlock.gif)
9
![](/Images/OutliningIndicators/InBlock.gif)
10
![](/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
11
![](/Images/OutliningIndicators/ExpandedBlockEnd.gif)
输出10000以内的完全数
又称完美数,它是指真因子之和等于自身的自然数
1
for (int i = 1; i <= 10000; i++)
2
{
3
int k = 0;
4
for (int j = 1; j <= i - 1; j++)
5
{
6
if ((i % j) == 0)
7
{
8
k += j;
9
}
10
}
11
if (k == i)
12
{
13
System.Console.WriteLine(i);
14
}
15
}
![](/Images/OutliningIndicators/None.gif)
2
![](/Images/OutliningIndicators/ExpandedBlockStart.gif)
3
![](/Images/OutliningIndicators/InBlock.gif)
4
![](/Images/OutliningIndicators/InBlock.gif)
5
![](/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
6
![](/Images/OutliningIndicators/InBlock.gif)
7
![](/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
8
![](/Images/OutliningIndicators/InBlock.gif)
9
![](/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
10
![](/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
11
![](/Images/OutliningIndicators/InBlock.gif)
12
![](/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
13
![](/Images/OutliningIndicators/InBlock.gif)
14
![](/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
15
![](/Images/OutliningIndicators/ExpandedBlockEnd.gif)
输出10000以内的相亲数
两个正整数,X的真因子之和等于Y的真因子之和
1
for (int i = 1; i <= 10000; i++)
2
{
3
int x = i;//X为初值
4
int y = 0;
5
for (int j = 1; j <= x - 1; j++)//计算X的真因子
6
{
7
if ((x % j) == 0)
8
{ y += j; }
9
}//Y=X的真因子之合
10
if (y == x)//完美数
11
{ continue; }
12
x = 0;
13
for (int j = 1; j <= y - 1; j++)//计算Y的真因子
14
{
15
if ((y % j) == 0)
16
{ x += j; }
17
}//X=Y的真因子之合
18
if (x == i)
19
{
20
System.Console.WriteLine("{0}--{1}", x, y);
21
}
22
}
![](/Images/OutliningIndicators/None.gif)
2
![](/Images/OutliningIndicators/ExpandedBlockStart.gif)
3
![](/Images/OutliningIndicators/InBlock.gif)
4
![](/Images/OutliningIndicators/InBlock.gif)
5
![](/Images/OutliningIndicators/InBlock.gif)
6
![](/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
7
![](/Images/OutliningIndicators/InBlock.gif)
8
![](/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
9
![](/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
10
![](/Images/OutliningIndicators/InBlock.gif)
11
![](/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
12
![](/Images/OutliningIndicators/InBlock.gif)
13
![](/Images/OutliningIndicators/InBlock.gif)
14
![](/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
15
![](/Images/OutliningIndicators/InBlock.gif)
16
![](/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
17
![](/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
18
![](/Images/OutliningIndicators/InBlock.gif)
19
![](/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
20
![](/Images/OutliningIndicators/InBlock.gif)
21
![](/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
22
![](/Images/OutliningIndicators/ExpandedBlockEnd.gif)
部分摘录自:http://www.cnblogs.com/shyleoking/articles/635591.html