平衡树模板的一部分？。。。

rt

merge

int merge(int rt1,int rt2){
	if(!rt1||!rt2)	return rt1|rt2;
	if(rk[rt1]<rk[rt2]){
		pushdown(rt1);
		son[rt][1]=merge(son[rt][1],rt2);
		pushup(rt1);
		return rt1;
	}
	else{
		pushdown(rt2);
		son[rt2][0]=merge(rt1,son[rt2][0]);
		pushup(rt2);
		return rt2;
	}
}

spilt

pair<int,int> spilt<int rt,int y>{
	pair<int,int> ans;
	if(rt==0){
		ans.first=ans.second=0;
		return ans;
	}
	if(sz[rt]>=y){
		ans=spilt(son[rt][0],y);
		son[rt][0]=ans.second;
		ans.second=rt;
	}
	else{
		ans=spilt(son[rt][1],y);
		son[rt][1]=ans.first;
		ans.first=rt;
	}
	pushup(rt);
	return ans;
}

newnode

int newnode(int x){
	tot++;
	key[tot]=x;
	sz[tot]=1;
	rk[tot]=rank();
	return tot;
}

find

int find(int k,int rt=top){
	pushdown(rt);
	if(sz[son[rt][0]]>=k)
		return find(k,son[rt][0]);
	k-=sz[son[rt][0]];
	if(k==1)	return key[rt];
	k--;
	return find(k,son[rt][1]);
}