HNOI2002 营业额统计 [Treap]

#include <bits/stdc++.h>

const int inf=0x3f3f3f3f;

int N,Ans;

struct Treap
{
    Treap *ch[2];
    int size,cnt,r,v;
    Treap(int x)
    {
        size=cnt=1;
        r=rand();
        v=x;
        ch[0]=ch[1]=NULL;
    }
    int cmp(int x)
    {
        if(x==v) return -1;
        return x>v;
    }
    void maintain()
    {
        size=cnt+((ch[0]==NULL)?0:ch[0]->size)+((ch[1]==NULL)?0:ch[1]->size);
    }
}*root;

void rotate(Treap* &o,int d)
{
    Treap *k=o->ch[d^1];
    o->ch[d^1]=k->ch[d];
    k->ch[d]=o;
    o->maintain(),k->maintain();
    o=k;
}

void insert(Treap* &o,int x)
{
    if(o==NULL) o=new Treap(x);
    else
    {
        if(o->v==x) ++(o->cnt);
        else
        {
            int d=o->cmp(x);
            insert(o->ch[d],x);
            if(o->ch[d]->r>o->r) rotate(o,d^1);
        }
    }
    o->maintain();
}

int upper(Treap *o,int x)
{
    if(o==NULL) return -inf;
    else if(o->cmp(x)!=0) return std::max(o->v,upper(o->ch[1],x));
    else return upper(o->ch[0],x);
}

int lower(Treap *o,int x)
{
    if(o==NULL) return inf;
    else if(o->cmp(x)!=1) return std::min(o->v,lower(o->ch[0],x));
    else return lower(o->ch[1],x);
}

inline int read()
{
    register int x=0,v=1;
    register char ch=getchar();
    while(!isdigit(ch))
    {
        if(ch==‘-‘) v=-1;
        ch=getchar();
    }
    while(isdigit(ch))
    {
        x=(x<<1)+(x<<3)+ch-‘0‘;
        ch=getchar();
    }
    return x*v;
}

int main()
{
    int t;
    N=read();
    for(register int i=1;i<=N;++i)
    {
        t=read();
        if(root==NULL) Ans+=t;
        else Ans+=std::min(lower(root,t)-t,t-upper(root,t));
        insert(root,t);
    }
    printf("%d\n",Ans);
    return 0;
}