浅谈fhq_treap

Posted 2021-01-27 hzf29721

class Fhq_Treap{
    private:
    int tot,son[100010][2],key[100010],val[100010],sz[100010];
    inline void updata(int u){
        sz[u]=sz[son[u][0]]+sz[son[u][1]]+1;
    }
    inline void build(int l,int r,int lst){
        if(r<l)
            return ;
        if(l==r){
            son[lst][lst<l]=l;
            key[l]=rand();
            val[l]=l;
            sz[l]=1;
            return ;
        }
        int mid=(l+r)>>1;
        son[lst][lst<mid]=mid;
        key[mid]=rand();
        val[mid]=mid;
        build(l,mid-1,mid);
        build(mid+1,r,mid);
        updata(mid);
    }
    inline void make_rev_tag(int u){
        rev[u]^=1;
        swap(son[u][0],son[u][1]);
    }
    inline void pushdown(int u){
        if(rev[u]){
            if(son[u][0])
                make_rev_tag(son[u][0]);
            if(son[u][1])
                make_rev_tag(son[u][1]);
            rev[u]=0;
        }
    }
    inline pair<int,int>split(int u,int k){
        if(!k)
            return make_pair(0,u);
        if(k==sz[u])
            return make_pair(u,0);
        pushdown(u);
        if(k<=sz[son[u][0]]){
            pair<int,int>res=split(son[u][0],k);
            son[u][0]=res.second;
            updata(u);
            return make_pair(res.first,u);
        }else{
            pair<int,int>res=split(son[u][1],k-sz[son[u][0]]-1);
            son[u][1]=res.first;
            updata(u);
            return make_pair(u,res.second);
        }
    }
    inline int merge(int x,int y){
        if(!x||!y)
            return x+y;
        pushdown(x);
        pushdown(y);
        if(key[x]<key[y]){
            son[x][1]=merge(son[x][1],y);
            updata(x);
            return x;
        }else{
            son[y][0]=merge(x,son[y][0]);
            updata(y);
            return y;
        }
    }
    public:
    int rt;
    bool rev[100010];
    inline void prepare(){
        tot=n;
        rt=(1+n)>>1;
        build(1,n,0);
    }
    inline void rever(int l,int r){
        pair<int,int>spl1=split(rt,r);
        pair<int,int>spl2=split(spl1.first,l-1);
        make_rev_tag(spl2.second);
        rt=merge(merge(spl2.first,spl2.second),spl1.second);
    }
    inline void print_ans(int u){
        if(!u)
            return ;
        pushdown(u);
        print_ans(son[u][0]);
        printf("%d ",val[u]);
        print_ans(son[u][1]);
    }
}F;