USACO 2.2 Subset Sums

TASK: subset
LANG: C++

Compiling...
Compile: OK

Executing...
   Test 1: TEST OK [0.000 secs, 3148 KB]
   Test 2: TEST OK [0.000 secs, 3148 KB]
   Test 3: TEST OK [0.000 secs, 3148 KB]
   Test 4: TEST OK [0.000 secs, 3148 KB]
   Test 5: TEST OK [0.000 secs, 3148 KB]
   Test 6: TEST OK [0.000 secs, 3148 KB]
   Test 7: TEST OK [0.000 secs, 3148 KB]

All tests OK.
 1 /*
 2 PROG: subset
 3 ID: jiafeim1
 4 LANG: C++
 5 */
 6 
 7 
 8 #include <iostream>
 9 #include <fstream>
10 
11 using namespace std;
12 
13 int n;
14 int total = 0;
15 int now_res = 0;
16 int upper;
17 unsigned long res[42][800]={0};
18 
19 int main()
20 {
21     std::ifstream fin("subset.in");
22     std::ofstream fout("subset.out");
23 
24     fin >> n;
25     upper = (n + 1) * n / 2;
26 
27     res[0][0] = 1;
28     if (upper % 2 == 0)
29     {
30         upper/=2;
31         for(int i = 1;i<=n;++i)
32             for(int sum = upper;sum>=0;--sum)
33             {   
34                 if(sum>=i&&res[i-1][sum-i]!=0)
35                     res[i][sum]=res[i-1][sum-i];
36                 if(res[i-1][sum]!=0)
37                     res[i][sum]+=res[i-1][sum];
38             }
39         fout<<res[n][upper]/2<<endl;
40     }
41     else
42     {
43         fout << 0 << endl;
44     }
45     fin.close();
46     fout.close();
47 
48 }
posted @ 2011-05-04 23:06  幻魇  阅读(244)  评论(0)  编辑  收藏  举报