FZUOJ Problem 2178 礼物分配

#include <iostream>
#include <algorithm>
#include <vector>
#include <cstdio>
#include <cstring>
using namespace std;

typedef __int64 LL;
const int INF = 1 << 30;
const int MAXN = 40;
vector<int> num[MAXN];
int vi[MAXN],wi[MAXN];

int main() {
   int n,T;
   scanf("%d",&T);
   while(T--) {
       scanf("%d",&n);
       for(int i = 0;i < n;++i) {
           scanf("%d",&vi[i]);
       }
       for(int i = 0;i < n;++i) {
           scanf("%d",&wi[i]);
       }

       for(int i = 0;i <= n;++i)
         num[i].clear();

       int n2 = n/2;
       int cnt,sum1 ,sum2,sum;
       for(int S = 0;S < 1 << n2; ++S) {
          cnt = 0,sum1 = 0,sum2 = 0;
          for(int i = 0;i < n2;++i) {
              if(S >> i & 1) {
                  sum1 += vi[i];
                  cnt++;
              } else {
                  sum2 += wi[i];
              }
          }
          num[cnt].push_back(sum1 - sum2);
       }

       for(int i = 0;i < n2;++i) {
           sort(num[i].begin(),num[i].end());
           num[i].erase(unique(num[i].begin(),num[i].end()),num[i].end());
       }

       int ans = INF;
       for(int S = 0;S < 1 << (n-n2);++S) {
           sum,cnt = 0,sum1 = 0,sum2 = 0;
           for(int i = 0;i < (n-n2);++i) {
               if(S >> i & 1) {
                   sum1 += vi[i+n2];
                   cnt++;
               } else {
                   sum2 += wi[i+n2];
               }
           }
           int t = n - n2 - cnt;
           sum = sum1 - sum2;    
           vector<int>::iterator iter;
           iter = lower_bound(num[t].begin(),num[t].end(),-sum);

           if(iter != num[t].end() && abs(*iter + sum) < ans)
               ans = abs(*iter + sum);

           if(iter != num[t].begin()) {
                --iter;
               if(abs(*iter + sum) < ans) ans = abs(*iter + sum);
           }
       }

        printf("%d\n",ans);
   }
   return 0;
}


/*


3
1 2 3
4 2 1

5
1 2 3 5 4
1 1 1 1 5

6
1 2 3 4 5 5
1 1 1 1 1 8

*/