rt。在下方完整代码的 18 行，给节点随机赋权值的时候，我写了两种写法：

//写法一
tree[p].val = rd();
//写法二
tree[p].val = rd()%114514;

唯一区别在于取模。但是写法一样例第 3 个输出随机抽风为 4，写法二却没事。

没开 long long，随机数用的是 mt19937。其它平衡树我是按照写法一写的，没抽过风，今天是第一次。问佬是什么原因？建议用哪种写法？

完整代码：

#include<bits/stdc++.h>
using namespace std;
int n,m,ntot = 0,root;
mt19937 rd(time(0));
stack<int> que;
bitset<50005> used;
struct node{
	int ls,rs,key,val,s;
}tree[50005];
void push_up(int p){
	tree[p].s = tree[tree[p].ls].s+tree[tree[p].rs].s+1;
	return;
}
int addnode(int key){
	int p = ++ntot;
	tree[p].ls = tree[p].rs = 0;
	tree[p].key = key;
	tree[p].val = rd()%114514;
	tree[p].s = 1;
	return p;
}
void build(){
	addnode(0),addnode(n+1);
	root = 1;
	tree[1].rs = 2;
	push_up(1);
	return;
}
void zig(int &p){
	int q = tree[p].ls;
	tree[p].ls = tree[q].rs,tree[q].rs = p,p = q;
	push_up(tree[p].rs),push_up(p);
	return;
}
void zag(int &p){
	int q = tree[p].rs;
	tree[p].rs = tree[q].ls,tree[q].ls = p,p = q;
	push_up(tree[p].ls),push_up(p);
	return;
}
void add(int &p,int key){
	if(!p){
		p = addnode(key);
	}else{
		if(tree[p].key > key){
			add(tree[p].ls,key);
			if(tree[tree[p].ls].val > tree[p].val){
				zig(p);
			}
		}else{
			add(tree[p].rs,key);
			if(tree[tree[p].rs].val > tree[p].val){
				zag(p);
			}
		}
	}
	push_up(p);
	return;
}
void del(int &p,int key){
	if(!p){
		return;
	}
	if(tree[p].key == key){
		if(tree[p].ls || tree[p].rs){
			if(!tree[p].rs || tree[tree[p].ls].val > tree[tree[p].rs].val){
				zig(p);
				del(tree[p].rs,key);
			}else{
				zag(p);
				del(tree[p].ls,key);
			}
		}else{
			p = 0;
		}
	}else{
		if(tree[p].key > key){
			del(tree[p].ls,key);
		}else{
			del(tree[p].rs,key);
		}
	}
	push_up(p);
	return;
}
int getprev(int p,int key){
	if(!p){
		return 0;
	}
	if(tree[p].key > key){
		return getprev(tree[p].ls,key);
	}else{
		return max(tree[p].key,getprev(tree[p].rs,key));
	}
}
int getnext(int p,int key){
	if(!p){
		return n+1;
	}
	if(tree[p].key < key){
		return getnext(tree[p].rs,key);
	}else{
		return min(tree[p].key,getnext(tree[p].ls,key));
	}
}
int main(){
	scanf("%d%d",&n,&m);
	build();
	while(m--){
		static char tpa;
		static int tpb;
		scanf(" %c",&tpa);
		if(tpa == 'R'){
			if(que.size()){
				del(root,que.top());
				used[que.top()] = 0;
				que.pop();
			}
			continue;
		}
		scanf("%d",&tpb);
		if(tpa == 'D'){
			add(root,tpb);
			used[tpb] = 1;
			que.push(tpb);
		}
		if(tpa == 'Q'){
			if(used[tpb]){
				puts("0");
			}else{
				printf("%d\n",getnext(root,tpb)-getprev(root,tpb)-1);
			}
		}
	}
	return 0;
}