ProjectEuler_problem68.cpp

//problem 68---
template<class COLLECTION>
bool cmp_arr(const COLLECTION& v1, const COLLECTION& v2) {
    for(int i=0; i<v1.size() ; i++) {
        if(v1[i]==v2[i])
            continue;
        if(v1[i]<v2[i])
            return true;
        else
            return false;

    }
    return false;
}
void solve68() {
    constexpr const int NG=5;
    constexpr const uint LIM=NG*3-NG;
    array<int,NG*3> NS;
    vector<array<int,NG*3>> SOLS;
    bitset<LIM> b(0);//which number has been used?
    for(int i=0; i < LIM ; i++) { //1
        b[i]=1;
        for(int j = 0 ; j < LIM ; j++) { //1
            if(!b[j]) {
                b[j]=1;
                for(int k = 0 ; k < LIM ; k++) { //1
                    if(!b[k]) {
                        b[k]=1;
                        int sum=i+j+k+3;
                        for(int l=0; l < LIM; l++) { //2
                            if(!b[l]) {
                                b[l]=1;
                                for(int l1=0;  l1 < LIM; l1++) { // 2
                                    if(!b[l1]) {
                                        b[l1]=1;
                                        int sum0 = l+k+l1+3;
                                        for(int l2=0; sum==sum0 && l2<LIM; l2++) { //3
                                            if(!b[l2]) {
                                                b[l2]=1;
                                                for(int l3=0;  l3<LIM; l3++) { //3
                                                    if(!b[l3]) {
                                                        b[l3]=1;
                                                        int sum1 = l2+l1+l3+3;
                                                        for(int l4=0; sum1==sum0 && l4<LIM; l4++) { //4
                                                            if(!b[l4]) {
                                                                b[l4]=1;
                                                                for(int l5=0;  l5<LIM; l5++) { //4
                                                                    if(!b[l5]) {
                                                                        b[l5]=1;
                                                                        int sum2 = l4+l3+l5+3;

                                                                        for(int l6=0;  l6<LIM; l6++) { //5
                                                                            int sum3=l6+l5+j+3;
                                                                            if(!b[l6] && sum3==sum2) {
                                                                                NS= {i+1,j+1,k+1,
                                                                                l+1,k+1,l1+1,
                                                                                l2+1,l1+1,l3+1,
                                                                                l4+1,l3+1,l5+1,
                                                                                l6+1,l5+1,j+1};
                                                                                //min element between elements of indices idx*3
                                                                                int min=0;
                                                                                for(int idx=3; idx<NG*3; idx+=3) {
                                                                                    if(NS[idx]<NS[min])
                                                                                        min = idx;
                                                                                }
                                                                                //rotate ns st the minimum element is at position 0
                                                                                rotate(NS.begin(),NS.begin()+min,NS.end() );
                                                                                SOLS.push_back(NS);
                                                                            }
                                                                        }//5 - l6
                                                                        b[l5]=0;
                                                                    }
                                                                }//4 - l5
                                                                b[l4]=0;
                                                            }
                                                        }//4 - l4

                                                        b[l3]=0;
                                                    }
                                                }//3 - l3
                                                b[l2]=0;
                                            }
                                        }//3 - l2
                                        b[l1]=0;
                                    }
                                }//2 - l1
                                b[l]=0;
                            }
                        }//2 - l
                        b[k]=0;
                    }
                }//1 -k
                b[j]=0;
            }
        }//1- j
        b[i]=0;
    }//1 -i

    auto ans = *std::max_element(SOLS.begin(),SOLS.end(),cmp_arr<array<int,NG*3>>);
    for(const auto& a : ans) {
        cout<<a;
    }
    cout<<endl;
}