[BZOJ4260]Codechef REBXOR(Trie)

Trie模板题。求出每个前缀和后缀的最大异或和区间，枚举断点就可。不知为何跑得飞快。

 #include<cstdio>
 #include<cstring>
 #include<algorithm>
 #define rep(i,l,r) for (int i=(l); i<=(r); i++)
 using namespace std;

 const int N=,M=N*;
 int n,nd,x,ans,a[N],pre[N],suf[N],ch[M][];

 void ins(int k){
     int x=;
     for (int i=; ~i; i--){
         if (!ch[x][(k>>i)&]) ch[x][(k>>i)&]=++nd;
         x=ch[x][(k>>i)&];
     }
 }

 int que(int k){
     int x=,res=;
     for (int i=; ~i; i--)
         if (ch[x][!((k>>i)&)]) res|=<<i,x=ch[x][!((k>>)&)];
             else x=ch[x][(k>>i)&];
     return res;
 }

 int main(){
     freopen("bzoj4260.in","r",stdin);
     freopen("bzoj4260.out","w",stdout);
     scanf("%d",&n); nd=; ins();
     rep(i,,n) scanf("%d",&a[i]);
     rep(i,,n-) x^=a[i],pre[i]=max(pre[i-],que(x)),ins(x);
     memset(ch,,sizeof(ch)); nd=; ins(); x=;
     for (int i=n; i>; i--) x^=a[i],suf[i]=max(suf[i+],que(x)),ins(x);
     rep(i,,n-) ans=max(ans,pre[i]+suf[i+]);
     printf("%d\n",ans);
     return ;
 }