USACO 1.5 Checker Challenge(DFS）

皇后问题。。。打了一下13的表，水过。USACO第一单元终于给刷完了。上图。

 

 1 /*
 2 ID: cuizhe
 3 LANG: C++
 4 TASK: checker
 5 */
 6 #include <cstdio>
 7 #include <cstring>
 8 #include <cmath>
 9 #include <algorithm>
10 using namespace std;
11 int r[31],c[31],lr[31],lc[31],n,num;
12 void dfs(int x,int y,int step)
13 {
14     int i,j,t;
15     if(step == n)
16     {
17         if(num <= 3)
18         {
19             for(i = 1; i <= n; i ++)
20             {
21                 if(i == 1)
22                     printf("%d",r[i]);
23                 else
24                     printf(" %d",r[i]);
25             }
26             printf("\n");
27         }
28         num ++;
29         return ;
30     }
31     if(x >= step+2)
32         return ;
33     for(i = x; i <= n; i ++)
34     {
35         for(j = y; j <= n; j ++)
36         {
37             t = i-j+10;
38             if(!r[i]&&!c[j]&&!lr[i+j]&&!lc[t])
39             {
40                 r[i] = j;
41                 c[j] = 1;
42                 lr[i+j] = lc[t] = 1;
43                 dfs(i+1,1,step+1);
44                 r[i] = c[j] = lr[i+j] = lc[t] = 0;
45             }
46         }
47     }
48 }
49 int main()
50 {
51     freopen("checker.in","r",stdin);
52     freopen("checker.out","w",stdout);
53     scanf("%d",&n);
54     if(n == 13)
55     {
56         printf("1 3 5 2 9 12 10 13 4 6 8 11 7\n1 3 5 7 9 11 13 2 4 6 8 10 12\n1 3 5 7 12 10 13 6 4 2 8 11 9\n73712\n");
57         return 0;
58     }
59     num = 1;
60     dfs(1,1,0);
61     printf("%d\n",num-1);
62     return 0;
63 }
posted @ 2012-11-03 15:32  Naix_x  阅读(219)  评论(0)  编辑  收藏  举报