Treap

http://www.nocow.cn/index.php/Treap_C%2B%2B

/*****************************************\
treap完成插入,删除,查找第K个数
询问x在序列中为名次,返回最小值
\*****************************************/
const int inf=~0U>>1;
class treap {
    struct node {
        int value,key,size;
        node(int v,node*n):value(v) {c[0]=c[1]=n;size=1;key=rand()-1;}
        void rz() {size=c[0]->size+c[1]->size+1;}
        node*c[2];
    }*root,*null;

    void rot(node*&t,bool d) {
        node*c=t->c[d];
        t->c[d]=c->c[!d];
        c->c[!d]=t;
        t->rz();c->rz();
        t=c;
    }

    void insert(node*&t,int x) {
        if(t==null)    {t=new node(x,null);return;}
        if(x==t->value) return;
        bool d=x>t->value;
        insert(t->c[d],x);
        if(t->c[d]->key<t->key) rot(t,d);
        else t->rz();
    }

    void Delete(node*&t,int x) {
        if(t==null) return;
        if(t->value==x) {
            bool d=t->c[1]->key<t->c[0]->key;
            if(t->c[d]==null) {
                delete t;
                t=null;
                return;
            }
            rot(t,d);
            Delete(t->c[!d],x);
        }
        else {
            bool d=x>t->value;
            Delete(t->c[d],x);
        }
        t->rz();
    }

    int select(node*t,int k) {
        int r=t->c[0]->size;
        if(k==r) return t->value;
        if(k<r) return select(t->c[0],k);
        return select(t->c[1],k-r-1);
    }

    int _min(node*t) {
        if(t==null) return inf;
        while(t->c[0]!=null) t=t->c[0];
        return t->value;
    }

    int rrank(node*t,int x) {
        if(t==null) return 0;
        int r=t->c[0]->size;
        if(x==t->value) return r;        
        if(x<t->value) return rrank(t->c[0],x);
        return r+1+rrank(t->c[1],x);
    }

    public:
        treap() {
            null=new node(0,0);null->size=0;null->key=inf;
            root=null;
        }
        int get_min() {
            return _min(root);
        }
        void ins(int x) {
            insert(root,x);
        }

        int sel(int k) {
            if(k>root->size) return -inf;
            return select(root,k-1);
        }

        int ran(int x) {
            return rrank(root,x);
        }
        void del(int x) {
            Delete(root,x);
        }    
}T;

void solve() {
    int i,j,k,x,tmp;
    char op[5];
    scanf("%s %d\n",op,&x);
    switch(op[0]) {
    case 'I':treap.ins(x);break;
    case 'D':treap.del(x);break;
    case 'K':tmp=treap.sel(x);if(tmp==-maxint)printf("invalid\n");else printf("%d\n",tmp);break;
    case 'C':printf("%d\n",treap.ran(x));break;
    }        
}

int main() {
    //freopen("in","r",stdin);
    int ca;scanf("%d\n",&ca);    
    while(ca--) solve();
    return 0;
}