E. XOR and Favorite Number （莫队板子题）

题目链接

复制代码

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
inline int read()
{
    int x=0,f=1;char ch=getchar();
    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
    while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
    return x*f;
}

/********************************************************************/

const int maxn = 1e5+7;
int n, m, k;
int a[maxn], belong[maxn];
ll ans[maxn], flag[maxn*20];    //注意这里的flag 要大大大大
ll now;

struct node{
    int l, r;
    int id;
}q[maxn];

bool cmp(node x, node y){
    if(belong[x.l] == belong[y.l])
        return x.r < y.r;
    return belong[x.l] < belong[y.l];
}

void Update(int x){
    now += flag[a[x]^k];
    flag[a[x]]++;
}

void Delete(int x){
    flag[a[x]]--;
    now -= flag[a[x]^k];
}

int main(){
    n = read(); m = read(); k = read();
    int sz = ceil(sqrt(n));
    for(int i = 1;i <= n;i++){
        a[i] = read();
        belong[i] = (i-1)/sz;
    }
    //前缀异或
    for(int i = 1;i <= n;i++){
        a[i] = a[i-1]^a[i];
    }
    for(int i = 1;i <= m;i++){
        q[i].l = read(); q[i].r = read();
        q[i].id = i;
    }
    sort(q+1, q+1+m, cmp);
    int l = 1, r = 0;
    now = 0;
    flag[0] = 1;
    for(int i = 1;i <= m;i++){
        int id = q[i].id;

        //while里面的顺序是不能随意更改的
        while(l < q[i].l){
            Delete(l-1);
            l++;
        }
        while(l > q[i].l){
            l--;
            Update(l-1);
        }
        while(r < q[i].r){
            r++;
            Update(r);
        }
        while(r > q[i].r){
            Delete(r);
            r--;
        }
        ans[id] = now;
    }
    for(int i = 1;i <= m;i++){
        cout << ans[i] << endl;
    }
    return 0;
}