【luogu P4462 [CQOI2018]异或序列】 题解

题目链接：https://www.luogu.org/problemnew/show/P4462

a_x+a_x-1+...+a_y = cnt_x+cnt_{y 这样把一段序列变成两段相加跑莫队。}

 #include <cstdio>
 #include <algorithm>
 #include <iostream>
 #include <cmath>
 using namespace std;
 const int maxn = ;
 int curR = , curL = , answer,a[maxn], ans[maxn], cnt[maxn], n, m, k, bl;
 struct query{
     int l,r,p;
 }q[maxn];

 bool cmp(const query &a, const query &b)
 {
     return (a.l/bl) == (b.l/bl) ? a.r<b.r : a.l<b.l;
 }

 inline void add(int pos)
 {
     cnt[a[pos]]++;
     answer+=cnt[a[pos]^k];
 }

 inline void remove(int pos)
 {
     cnt[a[pos]]--;
     answer-=cnt[a[pos]^k];
 }

 int main()
 {
     scanf("%d%d%d",&n,&m,&k);
     bl = sqrt(n);
     cnt[] = ;
     for(int i = ; i <= n; i++)
     {
         scanf("%d",&a[i]);
         a[i] ^= a[i-];
     }

     for(int i = ; i <= m; i++)
     {
         scanf("%d%d",&q[i].l,&q[i].r);
         q[i].p = i;
     }

     sort(q+,q++m,cmp);

     for(int i = ; i <= m; i++)
     {
         while(curL < q[i].l) remove(curL-),curL++;
         while(curL > q[i].l) curL--,add(curL-);
         while(curR < q[i].r) add(++curR);
         while(curR > q[i].r) remove(curR--);
         ans[q[i].p] = answer;
     }
     for(int i = ; i <= m; i++)
     printf("%d\n",ans[i]);
     return ;
 }