2025“钉耙编程”中国大学生算法设计暑期联赛（2）——子集 · znzryb

## 思路讲解

这个子集确实还可以，不是很难，就是卡一下这个折半搜索01树。

你用线性基做基本不会被卡。

## AC代码



::: 源代码

```cpp
// by Gospel_rock
// from template_cpp
#include <bits/stdc++.h>
#define all(vec) vec.begin(),vec.end()
#define pb push_back
#define EB emplace_back
#define EM emplace
#define FI first
#define SE second
#define pct __builtin_popcountll
#define ctz __builtin_ctzll
#define SZ(a) ((long long) a.size())
#define FOR(i, a, b) for (long long i = (a); i <= (b); ++i)
#define ROF(i, a, b) for (long long i = (a); i >= (b); --i)
#define debug(var) cerr << #var <<":"<<var<<"\n";
#define cend cerr<<"\n-----------\n"
#define lson(var) (var<<1)
#define rson(var) ((var<<1)+1)
#define fsp(x) fixed<<setprecision(x)

using namespace std;

using  ll = long long;using ull = unsigned long long;
using DB=double;using LD=long double;
// using i128 = __int128;
using pdd = pair<DB,DB>;using plb = pair<ll,bool>;
using pll = pair<ll,ll>;using vll=vector<ll>;using vb=vector<bool>;
using vdb = vector<DB>;using vc=vector<char>;
using tll = tuple<ll,ll,ll>;
using vpll = vector<pll>;using vtll = vector<tll>;
using arr3 = array<ll,3> ;using arr2 = array<ll,2>;
constexpr ll MAXN=(ll)1e6+10,INF=(ll)1e17+9; // 1e18+9也是素数
constexpr ll mod=(ll)1e9+7; // 998244353;
constexpr double eps=1e-8;const double pi=acos(-1.0);
ll N,M,Q,X,K,T,lT;

inline void __();
signed main()
{
	ios::sync_with_stdio(false);
	cin.tie(0);cout.tie(0);
	
	cin>>lT;
	while(lT--)
		__();
	return 0;
}
/*

*/
// https://www.luogu.com.cn/record/228289095 基础模版
// 检测合并功能 https://acm.hdu.edu.cn/contest/view-code?cid=1173&rid=23716
struct LB{
    using ll=long long;
    ll n;vector<ll> b;
    LB(ll n=62){
        this->n=n;
        b.assign(n+5,0);
    }
    void insert(ll x){
        for(int i=n;i>=0;--i){
            if(x>>i&1){
                if(b[i]){
                    x^=b[i];
                }else{
                    b[i]=x;
                    return;
                }
            }
        }
    }
    ll findmx(){
        ll res=0;
        for(int i=n;i>=0;--i){
            if((res^b[i]) > res){
                res^=b[i];
            }
        }
        return res;
    }
    void merge(const LB & t){
        for(int i=n;i>=0;--i){
            if(t.b[i]){
                insert(t.b[i]);
            }
        }
    }
};
inline void __(){
	cin>>N;
    vll A(N);
	FOR(i,1,N){
        cin>>A[i-1];
    }
    ll ans=0;
    function <void(ll,LB)> dfs=[&](ll idx,LB lb)->void{
        if(idx >= N) {
            ans=max(ans,lb.findmx());
            return;
        }
        LB llb=lb;lb.insert(A[idx]);llb.insert(A[idx]);
        dfs(idx+2,lb);
        dfs(idx+3,llb);
    };
    LB lb;
    dfs(0,lb);
    cout<<ans<<"\n";
}
/*
AC
https://acm.hdu.edu.cn/contest/view-code?cid=1173&rid=23716
*/
```


:::


## 心路历程（WA，TLE，MLE……）