Codeforces 1100 F - Ivan and Burgers

F - Ivan and Burgers

思路：线性基+贪心，保存线性基中每一位的最后一个

代码：

#pragma GCC optimize(2)
#pragma GCC optimize(3)
#pragma GCC optimize(4)
#include<bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define pi acos(-1.0)
#define LL long long
//#define mp make_pair
#define pb push_back
#define ls rt<<1, l, m
#define rs rt<<1|1, m+1, r
#define ULL unsigned LL
#define pll pair<LL, LL>
#define pli pair<LL, int>
#define pii pair<int, int>
#define piii pair<pii, int>
#define MIN(a, b) (a)<(b)?(a):(b)
#define MAX(a, b) (a)>(b)?(a):(b)
#define pdd pair<long double, long double>
#define mem(a, b) memset(a, b, sizeof(a))
#define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define fopen freopen("in.txt", "r", stdin);freopen("out.txt", "w", stout);
//head

const int N = 5e5 + 5;
int a[N], ans[N], base[20], pos[20];
piii Q[N];
void add(int p) {
    int x = a[p];
    for (int i = 19; i >= 0; i--) {
        if(x&(1<<i)) {
            if(!base[i]) {
                base[i] = x;
                pos[i] = p;
                return ;
            }
            if(p > pos[i]) swap(base[i], x), swap(pos[i], p);
            x ^= base[i];
        }
    }
}
int main() {
    int n, q;
    scanf("%d", &n);
    for (int i = 1; i <= n; i++) scanf("%d", &a[i]);
    scanf("%d", &q);
    for (int i = 1; i <= q; i++) {
        scanf("%d %d", &Q[i].fi.se, &Q[i].fi.fi);
        Q[i].se = i;
    }
    sort(Q+1, Q+1+q);
    int now = 1;
    for (int i = 1; i <= q; i++) {
        int L = Q[i].fi.se, R = Q[i].fi.fi;
        while(now <= R) add(now++);
        int res = 0;
        for (int i = 19; i >= 0; i--) if(pos[i] >= L) res = MAX(res, res^base[i]);
        ans[Q[i].se] = res;
    }
    for (int i = 1; i <= q; i++) printf("%d\n", ans[i]);
    return 0;
}