如題，testgirl的第47題，無論小弟我如何嘗試，
執行時間仍然會爆表
請問強者們，要怎麼做才能減少我的運算時間？
麻煩強者賜教
底下是題目和我的程式碼
題目：
Practice 04 (recursive function)
Given a integer N, print out the N! combination composed of first N upper letters.
The output answers should be in lexical order.
Hint: you may need arrays to assist you in the recursive process.
Input format:
One integer per line. The integers will range from 1 to 10.
Output format:
Print out all the combinations, one combination per line.
Between every case, you should print a line cotaining only '.' .
Example:
Input:
1
2
3
Output:
A
.
AB
BA
.
ABC
ACB
BAC
BCA
CAB
CBA
然後這是我的程式碼：
#include<stdio.h>
void re(int l,int n,int s[],int p[]);
int main()
{
int i,j,k,b=0;
int s[10],p[10];
int n,l;
while(scanf("%d",&l)!=EOF)
{
if(b==0)
b=1;
else
printf(".\n");
for(i=0;i<l;i++)
s[i]=i;
re(l,0,s,p);
}
return 0;
}
void re(int l,int n,int s[],int p[])
{
int i,j,h;
for(i=0;i<l;i++)
{
if(s[i]==-1)
continue;
p[n]=s[i];
s[i]=-1;
re(l,n+1,s,p);
s[i]=p[n];
}
if(n==l)
{
for(i=0;i<l;i++)
printf("%c",'A'+p[i]);
printf("\n");
}
}