洛谷 2234 [HNOI2002]营业额统计——treap（入门）

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<ctime>
using namespace std;
int rdn()
{
  int ret=0;bool fx=1;char ch=getchar();
  while(ch>‘9‘||ch<‘0‘){if(ch==‘-‘)fx=0;ch=getchar();}
  while(ch>=‘0‘&&ch<=‘9‘)ret=ret*10+ch-‘0‘,ch=getchar();
  return fx?ret:-ret;
}
int Mn(int a,int b){return a<b?a:b;}
const int N=32770,M=1e9;
int n,rt,tot,vl[N],c[N][2],rd[N],ans;
void rotate(int &cr,bool d)
{
  int v=c[cr][!d];
  c[cr][!d]=c[v][d]; c[v][d]=cr; cr=v;
}
void ins(int &cr,int k)
{
  if(!cr){cr=++tot; vl[cr]=k; rd[cr]=rand()%M; return;}
  int d;
  if(k<=vl[cr]) d=0, ins(c[cr][0],k);
  else d=1, ins(c[cr][1],k);
  if(rd[c[cr][d]]>rd[cr])rotate(cr,!d);
}
int fnd_pr(int cr,int k)
{
  if(!cr)return N;
  if(vl[cr]<=k)
    {
      int d=fnd_pr(c[cr][1],k);
      return d==N?cr:d;
    }
  return fnd_pr(c[cr][0],k);
}
int fnd_sc(int cr,int k)
{
  if(!cr)return N;
  if(vl[cr]>=k)
    {
      int d=fnd_sc(c[cr][0],k);
      return d==N?cr:d;
    }
  return fnd_sc(c[cr][1],k);
}
int main()
{
  srand(time(0)); n=rdn();
  for(int i=1,d;i<=n;i++)
    {
      d=rdn();
      if(i==1)ans=d;
      else
    {
      int u=fnd_pr(rt,d), v=fnd_sc(rt,d);
      if(u==N)ans+=vl[v]-d;
      else if(v==N)ans+=d-vl[u];
      else ans+=Mn(vl[v]-d,d-vl[u]);
    }
      ins(rt,d);
    }
  printf("%d\n",ans); return 0;
}