【Treap】[BZOJ 3224]Tyvj 1728 普通平衡树 & 非旋转实现

#include<cstdio>
#include<algorithm>
#include<cstring>
using namespace std;
#define maxn 2000005

struct Treap{
    Treap *l,*r;
    int fix,key,size;
    Treap(int key_){
        fix = rand();
        l = r = NULL;
        size = 1;
        key = key_;
    }

    inline void updata(){
        size=1+(l?l->size:0)+(r?r->size:0);
    }
}*root;
struct Droot{
    Treap *first, *second;
    Droot(){first = second = NULL;}
};
Droot D_NULL;
inline int Size(Treap *x){return x?x->size:0;}

Treap *Merge(Treap *A,Treap *B){
    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){
    if(!x)return D_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)-1);
        x->r=y.first;
        x->updata();
        y.first=x;
    }
    return y;
}

int Findkth(int k){
    Droot x=Split(root,k-1);
    Droot y=Split(x.second,1);
    Treap *ans=y.first;
    root=Merge(Merge(x.first,ans),y.second);
    return ans->key;
}

int Getkth(Treap *x,int v){
    if(!x)return 0;
    return v<=x->key?Getkth(x->l,v):Getkth(x->r,v)+Size(x->l)+1;
}

void Insert(int v){
    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){
    int pos = Getkth(root, k);
    Droot x=Split(root,pos);
    Droot y=Split(x.second,1);
    root=Merge(x.first,y.second);
}

int pre(int k){
    int pos = Getkth(root, k);
    Droot x = Split(root, pos-1);
    Droot y = Split(x.second, 1);
    Treap *ans = y.first;
    root=Merge(Merge(x.first,ans),y.second);
    return ans->key;
}

int bak(int k){
    int pos = Getkth(root, k+1);
    Droot x = Split(root, pos);
    Droot y = Split(x.second, 1);
    Treap *ans = y.first;
    root=Merge(Merge(x.first, ans), y.second);
    return ans->key;
}

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

int main(){
    scanf("%d",&M);
    while(M--){
        int x, o;
        scanf("%d %d", &o, &x);
        switch(o){
            case 1:Insert(x); break;
            case 2:Delete(x); break;
            case 3:printf("%d\n", Getkth(root, x)+1); break;
            case 4:printf("%d\n", Findkth(x)); break;
            case 5:printf("%d\n", pre(x)); break;
            case 6:printf("%d\n", bak(x)); break;
        }
    }
}