dfs全排列

#include<stdio.h>
#include<string.h>
#include<math.h>
#define maxn=1000;
int a[maxn],book[maxn],n,ans=0;
void dfs(int step){
int i;
if(step==n+1)
{
for(i=1;i<=n;i++)
printf("%d ",a[i]);
printf("\n");
ans++;
return ;
}

for(i=1;i<=n;i++){
if(book[i]==0){
a[step]=i;
book[i]=1;
dfs(step+1);
book[i]=0;
}
}
}
int main()
{
memset(book,0,sizeof(book));
memset(a,0,sizeof(a));
scanf("%d",&n);
int j=1;
dfs(j);
printf("\n%d\n",ans);
return 0;
}