FHQ_Treap 板子

namespace FHQ{
#define siz(x) ({Node *_a_ = x; _a_ == np ? 0 : _a_->sz; })
struct Node{
	Node *ls, *rs;
	char val; int pri;
	int sz;
	void updsz(){
		sz = 1 + siz(ls) + siz(rs);
	}
} cs[N];
void output(Node *root){
	if(root == np) return;
	output(root->ls);
	putchar(root->val);
#if DEBUG
	fflush(stdout);
#endif
	output(root->rs);
}
Node* merge(Node* sm, Node* bg){
	if(sm == np || bg == np) { return sm == np ? bg : sm; }
	if(sm->pri < bg->pri){
		sm->rs = merge(sm->rs, bg);
		sm->updsz();
		return sm;
	} else {
		bg->ls = merge(sm, bg->ls);
		bg->updsz();
		return bg;
	}
}
void splitrk(Node* root, int rk, Node*& ret1, Node*& ret2){
	if(root == np){
		ret1 = ret2 = np;
		return;
	}
	if(siz(root->ls) == rk-1){
		ret1 = root->ls;
		ret2 = root;
		root->ls = np;
		root->updsz();
	} else if(siz(root->ls) < rk-1){
		Node* r1, *r2;
		splitrk(root->rs, rk-siz(root->ls)-1, r1, r2);
		root->rs = r1;
		root->updsz();
		ret2 = r2;
		ret1 = root;
	} else {
		Node *r1, *r2;
		splitrk(root->ls, rk, r1, r2);
		root->ls = r2;
		root->updsz();
		ret1 = r1;
		ret2 = root;
	}
}
Node* nnod(char v){
	static int cnt = 0;
	cnt++;
	Node* p = &cs[cnt-1];
	p->ls = p->rs = np;
	p->val = v;
	p->pri = rand();
	p->sz = 1;
	return p;
}
}