区域赛系列一多边形划分
描述：
Give you a convex（凸边形）, diagonal n-3 disjoint divided into n-2 triangles(直线), for different number of methods, such as n=5, there are 5 kinds of partition method, as shown in Figure
输入：
The first line of the input is a n (1<=n<=1000), expressed n data set.
The next n lines each behavior an integer m (3<=m<=18), namely the convex edges.
输出：
For each give m,, output how many classification methods.
example output: Case #a : b
样例输入：
3
3
4
5
样例输出：
Case #1 : 1
Case #2 : 2
Case #3 : 5
提示：卡特兰数
程序代码：
#include<stdio.h>
int main()
{
int m,n,i,t;
int a[20];
a[3]=1;
a[4]=2;
a[5]=5;
for(i=5;i<18;i++)
a[i+1]=a[i]*(4*i-6)/i;
scanf("%d",&n);
t=1;
while(n--)
{
scanf("%d",&m);
printf("Case #%d : %d",t,a[m]);
t++;
printf("\n");
}
return 0;
}