莫队算法模版题
#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<cmath>
#include<algorithm>
using namespace std;
const int N=50005;
int n,m,k,a[N],block_size,ans[N],c[N];
struct Query{
int l,r,block,id;
friend bool operator<(Query A,Query B){return A.block<B.block||(A.block==B.block && A.r<B.r);}
}q[N];
void Solve(){
int L=1,R=0,Ans=0;
for(int i=1;i<=m;i++){
while(L<q[i].l){if(a[L])Ans-=2*c[a[L]]-1;c[a[L]]--;L++;}
while(L>q[i].l){L--;c[a[L]]++;if(a[L])Ans+=2*c[a[L]]-1;}
while(R<q[i].r){R++;c[a[R]]++;if(a[R])Ans+=2*c[a[R]]-1;}
while(R>q[i].r){if(a[R])Ans-=2*c[a[R]]-1;c[a[R]]--;R--;}
ans[q[i].id]=Ans;
}
}
int main(){
freopen("3781.in","r",stdin);
freopen("3781.out","w",stdout);
scanf("%d %d %d",&n,&m,&k);
block_size=(int)sqrt(m);
if(block_size<50)block_size=50;
for(int i=1;i<=n;i++){scanf("%d",&a[i]);if(a[i]>k)a[i]=0;}
for(int i=1;i<=m;i++){
scanf("%d %d",&q[i].l,&q[i].r);
q[i].block=(q[i].l+1)/block_size;
q[i].id=i;
}
sort(q+1,q+m+1);
Solve();
for(int i=1;i<=m;i++)printf("%d\n",ans[i]);
return 0;
}
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