bzoj 4260

设a[i]为前缀和，则i~j的异或和为a[j]^a[i]，对于2个只需把另一个当成后缀就可以了

求max(a[j]^a[i])的话就用tire维护就可以了

#include<bits/stdc++.h>
#define inc(i,l,r) for(int i=l;i<=r;i++)
#define dec(i,l,r) for(int i=l;i>=r;i--)
#define link(x) for(edge *j=h[x];j;j=j->next)
#define mem(a) memset(a,0,sizeof(a))
#define inf 1e9
#define ll long long
#define succ(x) (1<<x)
#define lowbit(x) (x&(-x))
#define NM 400000+5
using namespace std;
int read(){
    int x=0,f=1;char ch=getchar();
    while(!isdigit(ch)){if(ch=='-')f=-1;ch=getchar();}
    while(isdigit(ch))x=x*10+ch-'0',ch=getchar();
    return x*f;
}
const int m=31;
int n,a[NM],ans,_t,l[NM],r[NM];
struct node{
    node *c[2];
}N[(m+1)*NM],*o=N,*root;
void ins(int x){
    node *r=root;
    dec(i,m,0){
        int t=(1<<i)&x?1:0;
        if(!r->c[t])r->c[t]=++o;
        r=r->c[t];
    }
}
int find(int x){
    int s=0;node *r=root;
    dec(i,m,0){
        int t=(1<<i)&x?0:1;
        if(r->c[t]){
            s+=1<<i;
            r=r->c[t];
        }else r=r->c[t^1];
    }
    return s;
}
int main(){
    freopen("data.in","r",stdin);
    n=read();
    inc(i,1,n)a[i]=read();
    root=++o;ins(_t);
    inc(j,1,n){
    //    node *t=o;
        _t^=a[j];
        l[j]=max(l[j-1],find(_t));
        ins(_t);
    //    printf("%d ",o-N);
    }
    mem(N);root=o=N;_t=0;ins(_t);
    dec(i,n,1){
        _t^=a[i];
        r[i]=max(r[i-1],find(_t));
        ins(_t);
    }
    //inc(i,1,n)printf("%d ",l[i]);printf("
");
    //inc(i,1,n)printf("%d ",r[i]);printf("
");
    inc(i,1,n-1)ans=max(ans,l[i]+r[i+1]);
    printf("%d
",ans);
    return 0;
}