bzoj 1941 Hide and Seek

题目大意：

n个点，求每个点到其最远点距离-到其最近点距离（除自己之外）的最小值

思路：

对于估计函数的理解还不够深刻

 #include<iostream>
 #include<cstdio>
 #include<cstring>
 #include<cstdlib>
 #include<cmath>
 #include<algorithm>
 #include<queue>
 #include<vector>
 #include<map>
 #include<set>
 #define ll long long
 #define inf 2139062143
 #define MAXN 500100
 #define MOD 998244353
 #define rep(i,s,t) for(register int i=(s),i##__end=(t);i<=i##__end;++i)
 #define dwn(i,s,t) for(register int i=(s),i##__end=(t);i>=i##__end;--i)
 #define ren(x) for(register int i=fst[x];i;i=nxt[i])
 #define pb(i,x) vec[i].push_back(x)
 #define pls(a,b) (a+b)%MOD
 #define mns(a,b) (a-b+MOD)%MOD
 #define mul(a,b) (1LL*(a)*(b))%MOD
 using namespace std;
 inline int read()
 {
     int x=,f=;char ch=getchar();
     while(!isdigit(ch)) {if(ch=='-') f=-;ch=getchar();}
     while(isdigit(ch)) {x=x*+ch-'';ch=getchar();}
     return x*f;
 }
 int rt,n,Dim,ret1,ret2,ans;
 struct node{int mx[],mn[],d[],l,r;}tr[MAXN],g;
 bool operator < (const node a,const node b) {return a.d[Dim]<b.d[Dim];}
 struct kd_tree
 {
     void upd(int k)
     {
         node gl=tr[tr[k].l],gr=tr[tr[k].r];
         rep(i,,)
         {
             if(tr[k].l) tr[k].mn[i]=min(tr[k].mn[i],gl.mn[i]),tr[k].mx[i]=max(tr[k].mx[i],gl.mx[i]);
             if(tr[k].r) tr[k].mn[i]=min(tr[k].mn[i],gr.mn[i]),tr[k].mx[i]=max(tr[k].mx[i],gr.mx[i]);
         }
     }
     int build(int l,int r,int D)
     {
         int mid=l+r>>;Dim=D;nth_element(tr+l,tr+mid,tr+r+);
         rep(i,,) tr[mid].mn[i]=tr[mid].mx[i]=tr[mid].d[i];
         if(l<mid) tr[mid].l=build(l,mid-,D^);
         if(mid<r) tr[mid].r=build(mid+,r,D^);
         upd(mid);return mid;
     }
     int Get1(int k,int res=)
     {
         rep(i,,) res+=max(abs(g.d[i]-tr[k].mn[i]),abs(g.d[i]-tr[k].mx[i]));
         return res;
     }
     int Get2(int k,int res=)
     {
         rep(i,,) res+=max(,tr[k].mn[i]-g.d[i]);
         rep(i,,) res+=max(,g.d[i]-tr[k].mx[i]);return res;
     }
     int dis(int k,int res=) {rep(i,,) res+=abs(tr[k].d[i]-g.d[i]);return res;}
     void query(int k)
     {
         int dl1=,dr1=,dl2=inf,dr2=inf;
         ret1=max(ret1,dis(k));if(dis(k)) ret2=min(ret2,dis(k));
         if(tr[k].l) dl1=Get1(tr[k].l),dl2=Get2(tr[k].l);
         if(tr[k].r) dr1=Get1(tr[k].r),dr2=Get2(tr[k].r);
         if(dl1>dr1)
         {
             if(dl1>ret1)
             {
                 query(tr[k].l);
                 if(dr1>ret1||dr2<ret2) query(tr[k].r);
             }else
             {
                 if(dr2<ret2) query(tr[k].r);
                 if(dl2<ret2) query(tr[k].l);
             }
         }else
         {
             if(dr1>ret1)
             {
                 query(tr[k].r);
                 if(dl1>ret1||dl2<ret2) query(tr[k].l);
             }else
             {
                 if(dl2<ret2) query(tr[k].l);
                 if(dr2<ret2) query(tr[k].r);
             }
         }
     }
 }kd;
 int main()
 {
     n=read();rep(i,,n) tr[i].d[]=read(),tr[i].d[]=read();
     rt=kd.build(,n,),ans=inf;
     rep(i,,n)
     {
         g=tr[i],ret1=,ret2=inf;kd.query(rt);
         ans=min(ans,ret1-ret2);
     }
     printf("%d\n",ans);
 }