[BZOJ]3781: 小B的询问

莫队裸题，连我这种蒟蒻都可以一次AC

#include <cstdio>
#include <cmath>
#include <algorithm>
using namespace std;
inline char tc(void)
{
    static char fl[10001],*A=fl,*B=fl;
    return A==B?B=(A=fl)+fread(fl,1,10000,stdin),A==B?EOF:*A++:*A++;    
}
inline void read(int &a)
{
    a=0;static char c;
    while((c=tc())<'0'||c>'9');
    while(c>='0'&&c<='9')
        a=a*10+c-'0',c=tc();
    return ;
}
struct Y
{
    int l,r,h;      
    bool operator <(const Y&a) const
    {
        return l<a.l||l==a.l&&r<a.r;
    }
}q[50001];
int sl=1,sr,n,m,k,size,z[50001],sum[50001],l[50001],r[50001],now,ans[50001];
int main(void)
{
    register int i;
    read(n),read(m),read(k);
    for (i=1;i<=n;++i)
        read(z[i]);
    size=sqrt(n);
    for (i=1;i<=m;++i)
        read(l[i]),read(r[i]),q[i].l=(l[i]-1)/size+1,q[i].r=(r[i]-1)/size+1,q[i].h=i;
    sort(q+1,q+m+1);
    for (i=1;i<=m;++i)
    {
        while(sr<r[q[i].h]) now+=++sum[z[++sr]]*2-1;
        while(sr>r[q[i].h]) now-=sum[z[sr--]]--*2-1;
        while(sl<l[q[i].h]) now-=sum[z[sl++]]--*2-1;
        while(sl>l[q[i].h]) now+=++sum[z[--sl]]*2-1;
        ans[q[i].h]=now;
    }
    for (i=1;i<=m;++i)
        printf("%d\n",ans[i]);
    return 0;
}