E. XOR and Favorite Number （莫队板子题）

题目链接

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

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

 const int maxn = 1e5+;
 int n, m, k;
 int a[maxn], belong[maxn];
 ll ans[maxn], flag[maxn*];    //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 = ;i <= n;i++){
         a[i] = read();
         belong[i] = (i-)/sz;
     }
     //前缀异或
     for(int i = ;i <= n;i++){
         a[i] = a[i-]^a[i];
     }
     for(int i = ;i <= m;i++){
         q[i].l = read(); q[i].r = read();
         q[i].id = i;
     }
     sort(q+, q++m, cmp);
     int l = , r = ;
     now = ;
     flag[] = ;
     for(int i = ;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-);
             l++;
         }
         while(l > q[i].l){
             l--;
             Update(l-);
         }
         while(r < q[i].r){
             r++;
             Update(r);
         }
         while(r > q[i].r){
             Delete(r);
             r--;
         }
         ans[id] = now;
     }
     for(int i = ;i <= m;i++){
         cout << ans[i] << endl;
     }
     return ;
 }