poj 2034(dfs)

读清题意，暴力dfs即可。

提醒下自己：不会时多试试暴力，可能会有意想不到的结果。。。。有时候不要太谨慎。。

 1 // File Name: 2034.cpp
 2 // Author: Missa_Chen
 3 // Created Time: 2013年05月29日 星期三 19时27分06秒
 4 
 5 #include<iostream>
 6 #include<string>
 7 #include<algorithm>
 8 #include<cstdio>
 9 #include<cstring>
10 #include<cmath>
11 #include<queue>
12 #include<map>
13 #include<stack>
14 #include<set>
15 #include<cstdlib>
16 
17 using namespace std;
18 
19 #define LL long long
20 const int inf = 0x3f3f3f3f;
21 const int maxn = 1e4 + 5;
22 int n, m, d;
23 int p[maxn], ans[maxn];
24 void prime()
25 {
26     memset(p, 0, sizeof(p));
27     p[0] = p[1] = 1;
28     for (int i = 2; i < maxn; ++i)
29     {
30         if (p[i]) continue;
31         for (int j = i << 1; j < maxn; j += i)
32             p[j] = 1;
33     }
34 }
35 bool f[maxn];
36 int sum[11];
37 bool dfs(int step)
38 {
39     for (int i = 2; i <= d; ++i)
40         if (step - 1 >= i && !p[sum[i]])
41             return false;
42     if (step >= m - n + 2) return true;
43     for (int i = n; i <= m; ++i)
44     {
45         if (f[i]) continue;
46         for (int j = 2; j < step; ++j)
47             sum[j] -= ans[step - j];
48         for (int j = 2; j <= d; ++j)
49             sum[j] += i;
50         ans[step] = i;
51         f[i] = 1;
52         if(dfs(step + 1)) return true;
53         for (int j = 2; j < step; ++j)
54             sum[j] += ans[step - j];
55         for (int j = 2; j <= d; ++j)
56             sum[j] -= i;
57         f[i] = 0;
58     }
59     return false;
60 }
61 int main()
62 {
63     prime();
64     while (~scanf("%d%d%d",&n,&m,&d))
65     {
66         memset(f,0,sizeof(f));
67         memset(sum,0,sizeof(sum));
68         if (!n && !m && !d) break;
69         if (!dfs(1))
70         {
71             puts("No anti-prime sequence exists.");
72             continue;
73         }
74         printf("%d",ans[1]);
75         for (int i = 2; i <= m - n + 1; ++i)
76             printf(",%d",ans[i]);
77         printf("\n");
78     }
79     return 0;
80 }

 

posted @ 2013-05-29 20:17  Missa  阅读(350)  评论(0)  编辑  收藏  举报