四维偏序（K-D-Tree+rebuild）

其实只是放个代码，会K-D-Tree的同学看了就知道怎么rebuild了，其实也是很简单粗暴的……

单独再发一次吧，感觉把代码跟之前的一起发不知道啥时候就找不到了……

#include<bits/stdc++.h>
#define N 50010
#define inf 1000000009
#define lson (t1[o].l)
#define rson (t1[o].r)
using namespace std;
typedef long long ll;
int n,m,q[N],rt,dis,top=0;int tot=0,F;
inline int read(){
    int f=1,x=0;char ch;
    do{ch=getchar();if(ch=='-')f=-1;}while(ch<'0'||ch>'9');
    do{x=x*10+ch-'0';ch=getchar();}while(ch>='0'&&ch<='9');
    return f*x;
}int ans=0;
struct Point{
    int d[4],maxv[4],minv[4],l,r,f,size,v,ma;
    inline int& operator [] (int x){return d[x];}
    inline int in(){for(int i=0;i<4;i++)d[i]=read();}
}t1[N],t2[N],it;
bool cmp(int a,int b){return t1[a][F]<t2[b][F];}
bool operator < (Point a,Point b){
    for(int i=0;i<=3;i++){
        if(a.d[i]<b.d[i])return 1;
        if(a.d[i]>b.d[i])return 0;
    }
    return 0;
}
inline void pushup(int o){
    for(int i=0;i<=3;i++){
        t1[o].minv[i]=min(t1[o].d[i],min(t1[lson].minv[i],t1[rson].minv[i]));
        t1[o].maxv[i]=max(t1[o].d[i],max(t1[lson].maxv[i],t1[rson].maxv[i]));
    }
    t1[o].ma=max(t1[o].v,max(t1[lson].ma,t1[rson].ma));
    t1[o].size=t1[lson].size+t1[rson].size+1;
}
    int build(int l,int r,int f){
        int mid=(l+r)>>1;F=f;
        nth_element(q+l,q+mid,q+r+1,cmp);
        int o=q[mid];t1[o].f=f;lson=0;rson=0;
        if(l<mid)lson=build(l,mid-1,(f+1)%4);
        if(r>mid)rson=build(mid+1,r,(f+1)%4);
        pushup(o);return o;
    }
    void dfs(int o){
        if(!o)return;q[++top]=o;
        dfs(lson);dfs(rson);
    }
    void rebuild(int &o){
        top=0;dfs(o);
        o=build(1,top,t1[o].f);
    }
    inline int newnode(int f){
        int o=++tot;t1[tot].f=f;t1[o]=it;
        for(int i=0;i<=3;i++)t1[o].minv[i]=t1[o].maxv[i]=t1[o][i];
        t1[o].ma=t1[o].v;t1[o].size=1;
        return o;
    }
    void ins(int &o,int f){
        if(!o){o=newnode(f);return;}
        if(t1[o][f]<it[f]){
            ins(lson,(f+1)%4);
            pushup(o);
            if(t1[lson].size>t1[o].size*0.75)rebuild(o);
        }
        else{
            ins(rson,(f+1)%4);
            pushup(o);
            if(t1[rson].size>t1[o].size*0.75)rebuild(o);
        }
    }
    inline int check(int o){
        if(!o)return 0;int _=0;
        for(int i=0;i<=3;i++)if(t1[o].maxv[i]<=it.d[i])_++;
        if(_==4)return _;
         _=1;
        for(int i=0;i<=3;i++)if(t1[o].minv[i]>it[i])_=0;
        return _;
    }
    inline int calcdis(Point x,Point y){
        for(int i=0;i<=3;i++)if(x[i]>y[i])return 0;
        return x.v;
    }
    void query(int o){
        ans=max(calcdis(t1[o],it),ans);
        int dl=check(lson),dr=check(rson);
        if(dl==4)ans=max(ans,t1[lson].ma);
        else if(dl&&ans<t1[lson].ma)query(lson);
        if(dr==4)ans=max(ans,t1[rson].ma);
        else if(dr&&ans<t1[rson].ma)query(rson);
    }
int main(){
    n=read();
    for(int i=0;i<=3;i++)t1[0].minv[i]=inf,t1[0].maxv[i]=-inf;
    t1[0].ma=-inf;
    for(int i=1;i<=n;i++){
        t2[i].in();t2[i].v=1;
    }
    sort(t2+1,t2+n+1);
    int _=0;
    for(int i=1;i<=n;i++){
        ans=0;it=t2[i];
        query(rt);
        t2[i].v+=ans;it=t2[i];
        _=max(_,t2[i].v);ins(rt,0);
    }
    printf("%d
",_);
}