To xor or not to xor SGU

To xor or not to xor

SGU - 275

线性基求异或最大值~

#include <bits/stdc++.h>
using namespace std;
#define LL  long long
const int maxn = 110;
LL a[maxn], Bin[maxn];
int now;
void init(){
    Bin[0] = 1;
    for(int i = 1; i <= 61; i++) Bin[i] = Bin[i-1] << 1;
}

void gauss(int n){
    now = 1;
    for(int i = 61; i >= 0; i--) {
        int j = now;
        while(j <= n && !(a[j] & Bin[i])) j++;
        if(j == n+1) continue;
        if(j != now) swap(a[j], a[now]);
        for(int k = 1; k <= n; k++) if(k != now){
            if(a[k] & Bin[i]) a[k] ^= a[now];
        }
        now++;
    }
    now--;
}

LL query(){
    LL ans = 0;
    for(int i = 1; i <= now; i++) ans ^= a[i];
    return ans;
}

 
int main(){
    init();
    int n;
    scanf("%d", &n);
    for(int i = 1;  i <= n; i++) scanf("%lld", &a[i]);
    gauss(n);
    printf("%lld
", query());
}