题目传送门:http://codeforces.com/contest/665/problem/E
给你长度n的数组,然后问你有多少个区间,区间异或和大于等于k
区间异或和,一看就是01字典树,然后就是在01字典树上如何判断大于等于k咯,可以把k也每一位是0是1讨论,并且每个节点上记录放进去了多少个前缀,查询的时候就是当前查询的位数上是0是1和k这一位上是0是1分类讨论即可
代码:
#include <map>
#include <set>
#include <stack>
#include <queue>
#include <cmath>
#include <string>
#include <vector>
#include <cstdio>
#include <cctype>
#include <cstring>
#include <sstream>
#include <cstdlib>
#include <iostream>
#include <algorithm>
#pragma comment(linker, "/STACK:102400000,102400000")
using namespace std;
#define MAX 1000005
#define MAXN 6005
#define maxnode 15
#define sigma_size 30
#define lson l,m,rt<<1
#define rson m+1,r,rt<<1|1
#define lrt rt<<1
#define rrt rt<<1|1
#define middle int m=(r+l)>>1
#define LL long long
#define ull unsigned long long
#define mem(x,v) memset(x,v,sizeof(x))
#define lowbit(x) (x&-x)
#define pii pair<int,int>
#define bits(a) __builtin_popcount(a)
#define mk make_pair
#define limit 10000
//const int prime = 999983;
const int INF = 0x3f3f3f3f;
const LL INFF = 0x3f3f;
const double pi = acos(-1.0);
//const double inf = 1e18;
const double eps = 1e-8;
const LL mod = 1e9+7;
const ull mx = 133333331;
/*****************************************************/
inline void RI(int &x) {
char c;
while((c=getchar())<'0' || c>'9');
x=c-'0';
while((c=getchar())>='0' && c<='9') x=(x<<3)+(x<<1)+c-'0';
}
/*****************************************************/
int sum[MAX];
int val[32*MAX];
int ch[32*MAX][2];
int num[32*MAX];
int sz;
int n,k;
void init(){
sz=1;
mem(ch[0],0);
}
void inser(int a){
int u=0;
for(int i=30;i>=0;i--){
int c=((a>>i)&1);
if(!ch[u][c]){
mem(ch[sz],0);
num[sz]=0;
val[sz]=0;
ch[u][c]=sz++;
}
u=ch[u][c];
num[u]++;
}
val[u]=a;
}
int query(int a){
int u=0;
int ret=0;
for(int i=30;i>=0;i--){
int c=((a>>i)&1);
int d=((k>>i)&1);
if(ch[u][c^1]){
if(d==1) u=ch[u][c^1];
else{
ret+=num[ch[u][c^1]];
if(ch[u][c]) u=ch[u][c];
else return ret;
}
}
else{
if(d==1) return ret;
else{
if(ch[u][c]) u=ch[u][c];
else return ret;
}
}
}
return ret+num[u];
}
int main(){
//freopen("in.txt","r",stdin);
while(cin>>n>>k){
sum[0]=0;
LL ans=0;
init();
inser(sum[0]);
for(int i=1;i<=n;i++){
int a;
scanf("%d",&a);
sum[i]=sum[i-1]^a;
ans+=query(sum[i]);
inser(sum[i]);
}
cout<<ans<<endl;
}
return 0;
}