SRM 489 D2 500 BuyingFlowers

#include <algorithm>
#include <iostream>
#include <sstream>
#include <string>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <cstdio>
#include <cstdlib>
#include <cctype>
#include <cmath>
using namespace std;
typedef long long LL;
#define FOR(k,a,b) for(int k(a); k < (b); ++k)
#define REP(k,a) for(int k=0; k < (a); ++k)


class BuyingFlowers {
public:
    int buy(vector <int> roses, vector <int> lilies) {
        vector<int> bestChoice(320001,20000000);
        REP(i,320001)
        {
            for(int j=1;j*j<=i;++j)
                if(!(i%j))
                {
                    bestChoice[i]=(i/j-j);
                }
        }
        int res=-1;
        int n=roses.size();
        FOR(i,1,1<<n)
        {
            int roseNum=0,LilNum=0;
            REP(j,n)
            {
                if(1<<j & i)
                {
                    roseNum+=roses[j];
                    LilNum+=lilies[j];
                }
            }
            if(abs(roseNum-LilNum)<2 && (bestChoice[roseNum+LilNum]<res || res==-1))
            {
                res=bestChoice[roseNum+LilNum];
            }
        }
        return res;
    }

};