BZOJ 4627 回转寿司

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#define maxn 100500
using namespace std;
long long n,l,r,a[maxn],b[maxn],hash[maxn],tot=0,ans=0;
long long ls[maxn*40],rs[maxn*40],sum[maxn*40],root[maxn],cnt=0;
void build(long long last,long long &now,long long left,long long right,long long pos)
{
    now=++tot;sum[now]=sum[last]+1;
    if (left==right) return;
    long long mid=(left+right)>>1;
    ls[now]=ls[last];rs[now]=rs[last];
    if (pos<=mid) build(ls[last],ls[now],left,mid,pos);
    else build(rs[last],rs[now],mid+1,right,pos);
    sum[now]=sum[ls[now]]+sum[rs[now]];
}
long long ask(long long last,long long now,long long left,long long right,long long l,long long r)
{
    if ((left==l) && (right==r)) return sum[now]-sum[last];
    long long mid=(left+right)>>1;
    if (r<=mid) return ask(ls[last],ls[now],left,mid,l,r);
    else if (l>=mid+1) return ask(rs[last],rs[now],mid+1,right,l,r);
    else return ask(ls[last],ls[now],left,mid,l,mid)+ask(rs[last],rs[now],mid+1,right,mid+1,r);
}
int main()
{
    scanf("%lld%lld%lld",&n,&l,&r);
    for (long long i=1;i<=n;i++)
    {
        scanf("%lld",&a[i]);
        a[i]+=a[i-1];b[i]=a[i];hash[++cnt]=a[i];
    }
    sort(hash+1,hash+cnt+1);cnt=unique(hash+1,hash+cnt+1)-hash-1;
    for (long long i=1;i<=n;i++) a[i]=lower_bound(hash+1,hash+cnt+1,a[i])-hash;
    for (long long i=1;i<=n;i++) build(root[i-1],root[i],1,n,a[i]);
    for (long long i=1;i<=n;i++)
    {
        long long lb=b[i-1]+l,rb=b[i-1]+r;
        lb=lower_bound(hash+1,hash+cnt+1,lb)-hash;
        rb=lower_bound(hash+1,hash+cnt+1,rb)-hash;
        if (hash[rb]!=b[i-1]+r) rb--;
        if (lb>rb) continue;    
        ans+=ask(root[i-1],root[n],1,n,lb,rb);
    }
    printf("%lld\n",ans);
    return 0;
}