Educational Codeforces Round 12 E. Beautiful Subarrays trie求两异或值大于等于k对数

[b]E. Beautiful Subarrays[/b]

One day, ZS the Coder wrote down an array of integers a with elements a1,  a2,  ...,  an.

A subarray of the array a is a sequence al,  al  +  1,  ...,  ar for some integers (l,  r) such that 1  ≤  l  ≤  r  ≤  n. ZS the Coder thinks that a subarray of a is beautiful if the bitwise xor of all the elements in the subarray is at least k.

Help ZS the Coder find the number of beautiful subarrays of a!

[b]Input[/b]
The first line contains two integers n and k (1 ≤ n ≤ 106, 1 ≤ k ≤ 109) — the number of elements in the array a and the value of the parameter k.

The second line contains n integers ai (0 ≤ ai ≤ 109) — the elements of the array a.

[b]Output[/b]
Print the only integer c — the number of beautiful subarrays of the array a.

[b]Examples[/b]

[b]input[/b]

3 1
1 2 3

[b]output[/b]

5

[b]题意：[/b]
　　
　　给你n个数的序列，问你多少区间的异或值大于等于k
　
[b]题解：[/b]
　　
　　对于每一个前缀我们插入trie中,
　　询问当前前缀与之前前缀的异或值大于等于k就好

#include<bits/stdc++.h>
using namespace std;
const int maxn = 2e7+6;
struct Tri
{
int ch[maxn][2];
int sz[maxn];
int tot;
void init()
{
memset(ch,0,sizeof(ch));
memset(sz,0,sizeof(sz));
tot=2;
}
void insert(int x)
{
int u=1;sz[u]++;
for(int i=30;i>=0;i--)
{
int p = (x>>i)&1;
if(!ch[u][p])ch[u][p]=tot++;
u=ch[u][p]; sz[u]++;
}
}
int get(int x,int y)
{
int u=1;
long long ans = 0;
for(int i=30;i>=0;i--)
{
int p = (x>>i)&1^1;
int q = (y>>i)&1;
if(q==0)ans+=sz[ch[u][p]],u=ch[u][p^1];
else u=ch[u][p];
if(u==1) return ans;
}
return ans+sz[u];
}
}T;
int main()
{
T.init();
int n,k;
scanf("%d%d",&n,&k);
int pre = 0;
long long ans = 0;
T.insert(0);
for(int i=1;i<=n;i++)
{
int x;scanf("%d",&x);
pre^=x;
ans+=T.get(pre,k);
T.insert(pre);
}
cout<<ans<<endl;
return 0;
}