HDU 4671 Partition(定理题)

题目链接

这题，明显考察搜索能力。。。在中文版的维基百科中找到了公式。

 1 #include <cstdio>
 2 #include <cstring>
 3 #include <string>
 4 #include <algorithm>
 5 using namespace std;
 6 #define MOD 1000000007
 7 #define LL __int64
 8 LL dp[200001];
 9 int que[1001],flag[1001];
10 int main()
11 {
12     int i,n,t,j,num;
13     LL x;
14     num = 0;
15     for(i = 0;;i ++)
16     {
17         t = (3*i*i - i)/2;
18         if(t > 300000) break;
19         flag[num] = i;
20         que[num++] = t;
21         t = (3*i*i + i)/2;
22         flag[num] = i;
23         que[num++] = t;
24     }
25     dp[1] = 1;dp[2] = 2;
26     dp[0] = 1;
27     for(i = 3;i <= 100000;i ++)
28     {
29         for(j = 1;j <= 895;j ++)
30         {
31             if(que[j] > i)
32             break;
33             else
34             x = dp[i-que[j]];
35             if(flag[j]%2 == 1)
36             {
37                 dp[i] = (dp[i] + x)%MOD;
38             }
39             else
40             {
41                 dp[i] = (dp[i] - x)%MOD;
42                 if(dp[i] < 0)
43                 dp[i] += MOD;
44             }
45         }
46     }
47     scanf("%d",&t);
48     while(t--)
49     {
50         scanf("%d",&n);
51         printf("%I64d\n",dp[n]);
52     }
53     return 0;
54 }

 

posted @ 2013-08-06 19:08  Naix_x  阅读(240)  评论(0)  编辑  收藏  举报