fhq treap最终模板

新学习了fhq treap，厉害了

先贴个神犇的版，

from memphis

/*
    Treap[Merge,Split]
    by Memphis
*/

#include<cstdio>
#include<algorithm>
#include<cstring>
#include<ctime>
using namespace std;
#define maxn 2000005
#define rep(i,x,y) for(int i=x;i<=y;++i)
#define dep(i,x,y) for(int i=x;i>=y;--i)

struct Treap{
    Treap *l,*r;
    int fix,key,size;
    Treap(int key_):fix(rand()),key(key_),l(NULL),r(NULL),size(){}

    inline void updata(){
        size=+(l?l->size:)+(r?r->size:);
    }
}*root;
typedef pair<Treap*,Treap*> Droot;//用来Split返回两个根 

inline int Size(Treap *x){return x?x->size:;}//这样求size可以防止访问空指针 

Treap *Merge(Treap *A,Treap *B){//合并操作
    if(!A)return B;
    if(!B)return A;
    if(A->fix<B->fix){
        A->r=Merge(A->r,B);
        A->updata();
        return A;
    }else{
        B->l=Merge(A,B->l);
        B->updata();
        return B;
    }
}

Droot Split(Treap *x,int k){//拆分操作
    if(!x)return Droot(NULL,NULL);
    Droot y;
    if(Size(x->l)>=k){
        y=Split(x->l,k);
        x->l=y.second;
        x->updata();
        y.second=x;
    }else{
        y=Split(x->r,k-Size(x->l)-);
        x->r=y.first;
        x->updata();
        y.first=x;
    }
    return y;
}

Treap *Build(int *a){//建造操作
    static Treap *stack[maxn],*x,*last;
    int p=;
    rep(i,,a[]){
        x=new Treap(a[i]);
        last=NULL;
        while(p && stack[p]->fix>x->fix){
            stack[p]->updata();
            last=stack[p];
            stack[p--]=NULL;
        }
        if(p) stack[p]->r=x;
        x->l=last;
        stack[++p]=x;
    }
    while(p) stack[p--]->updata();
    return stack[];
}

int Findkth(int k){//查找第K小
    Droot x=Split(root,k-);
    Droot y=Split(x.second,);
    Treap *ans=y.first;
    root=Merge(Merge(x.first,ans),y.second);
    return ans->key;
}

int Getkth(Treap *x,int v){//询问一个数是第几大
    if(!x)return ;
    return v<x->key?Getkth(x->l,v):Getkth(x->r,v)+Size(x->l)+;
}

void Insert(int v){//插入操作
    int k=Getkth(root,v);
    Droot x=Split(root,k);
    Treap *n=new Treap(v);
    root=Merge(Merge(x.first,n),x.second);
}

void Delete(int k){//删除操作
    Droot x=Split(root,k-);
    Droot y=Split(x.second,);
    root=Merge(x.first,y.second);
}

int a[maxn],M,x,y;

int main(){
    freopen("bst.in","r",stdin);
    freopen("bst.out","w",stdout);

    scanf("%d",a);
    rep(i,,a[]) scanf("%d",a+i);
    sort(a+,a++a[]);
    root=Build(a);

    scanf("%d",&M);
    while(M--){
        char ch=getchar();
        while(ch!='Q' && ch!='A' && ch!='D') ch=getchar();
        scanf("%d",&x);
        if(ch=='Q') printf("%d\n",Findkth(x));
        if(ch=='A') Insert(x);
        if(ch=='D') Delete(x);
    }
}   

未完待续～～～