sdnu1592 easy problem（線性基）

Description

Albert_s has a multiset S, this question requires you to find a subset T of S that maximizes the expression of xor xor xor ​.

Input

The first line contains the integer indicating to the size of S.

The second line contains integer 、、、​ indicating the element in S.

Output

Output the maximum value of xor xor xor ​.

Sample Input

4
5 2 8 2

Sample Output

15

得 我孤陋寡聞 這題涼了

線性基：

https://www.cnblogs.com/yangsongyi/p/10692292.html

模板：

void ins(ll x)
{
    for(int i = 52 ; i >= 0 ; i-- )
    {
        if(!( x >> (1ll * i))) continue ;
        if(!p[i])
        {
            p[i] = x ;
            break ;
        }
        x = x ^ p[i] ;
    }
}

求完線性基後，貪心求異或最大值，高位數字的貢獻要大於它後面所有地位數字的貢獻，當前位數上的數異或答案後使得答案更大時，就更新

太菜了太菜了

#include <bits/stdc++.h>
#include <bitset>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
const int inf = 0x3f3f3f3f;
const int N = 60;
const int mod = 998244353;

ll s, p[N];

void ins(ll x)
{
    for(int i = 52; i >= 0; --i)
    {
        if(!(x >> (1ll * i)))
            continue;
        if(!p[i])
        {
            p[i] = x;
            break;
        }
        x ^= p[i];
    }
}

int main()
{
    int n;
    while(~scanf("%d", &n))
    {
        memset(p, 0, sizeof(p));
        for(int i = 1; i <= n; ++i)
        {
            scanf("%lld", &s);
            ins(s);
        }
        ll ans = 0;
        for(int i = 52; i >= 0; --i)
        {
            if((ans ^ p[i]) > ans)
                ans ^= p[i];
        }
        cout<<ans<<'\n';
    }
    return 0;
}