输出1——n的排列（深度优先搜索）

样例输入：

3

样例输出：

123
132
213
231
312
321

 1 #include <stdio.h>
 2 int n;
 3
 4 void dfs(int step,int* a,int* book)
 5 {
 6     int i;
 7     if(step == n)
 8     {
 9         for(i = 0;i < n;i++)
10         {
11             printf("%d",a[i]);
12         }
13         printf("\n");
14         return ;
15     }
16
17     for(i = 0;i < n;i++)
18     {
19         if(book[i] == 0)
20         {
21             a[step] = i+1;
22             book[i] = 1;
23             dfs(step+1,a,book);
24             book[i] = 0;
25         }
26     }
27 }
28 int main()
29 {
30     scanf("%d",&n);
31     int a[n+1],book[n+1],i;
32     for(i = 0;i < n;i++)
33     {
34         a[i] = 0;
35         book[i] = 0;
36     }
37     dfs(0,a,book);
38     return 0;
39 }