并查集加线段树合并
线下测试点1数据可以过，其他在线ide也能正常输出，但是提交和洛谷的ide都无法输出qwq 5WA 5RE 代码如下

#include<bits/stdc++.h>
using namespace std;
const int N = 2e5+100;

int n, m, q_op;
int fa[N],root[N*4], ls[N*4], rs[N*4]; 
int tot, sum[N*4];
int v[N];
int id_to[N];
int read()
{
	int x = 0, f = 1;char ch = getchar();
	while(ch<'0'||ch>'9') {if(ch == '-') f = -1;ch = getchar();	}
	while(ch>='0'&&ch<='9'){x = x*10+ch-'0'; ch = getchar();}
	return x*f;
}   

int merge(int now, int lst, int l, int r)//线段树合并模板，now 当前节点 lst 上一个节点 
{
	if(!now||!lst) return now | lst; 
	if(l == r)
	{
		sum[now] +=sum[lst];
		return now;
	 } 
	 int mid = (l+r)>>1;
	 ls[now] = merge(ls[now], ls[lst], l,mid ), rs[now] = merge(rs[now], rs[lst],mid+1, r);
	 sum[now]+=sum[lst];
	 return now;
 } 
void change(int l, int r, int p, int &tr, int v)
{
	if(!tr) tr = ++ tot;
	sum[tr]+=v;
	if(l == r) return;
	int mid = (l+r)>>1;
	if(p<=mid) change(l, mid, p, ls[tr], v);
	else change(mid+1, r, p, rs[tr], v);
}
int find(int x)
{
	if(x!=fa[x]) fa[x] = find(fa[x]);
	return fa[x];
}
int search(int tr, int kk, int l, int r)
{
	if(sum[tr]<kk) return -1;
	if(l == r) return l;
	int mid = (l+r)>>1;
	if(sum[ls[tr]]>=kk) return search(ls[tr], kk, l, mid);
	else return search(rs[tr], kk-sum[ls[tr]], mid+1, r);
}
int main()
{
	n = read(), m = read();
	for(int i = 1; i<=n; i++)
	{
		v[i] = read();
		id_to[v[i]] = i;
		change(1, n, v[i],root[i],1  );
	}
	
	for(int i = 1; i<=n; i++) fa[i] = i;
	for(int i = 1; i<=m; i++)
	{
		int u, v;
		u = read(), v = read();
		int pp = find(u);
		int qq = find(v);
		if(pp == qq) continue;
		fa[qq] = pp;
		root[qq] = merge(root[pp], root[qq], 1, n);
	}
	q_op = read();
	for(int i = 1; i<=q_op; i++)
	{
		char op;
		scanf("%c ", &op);
		if(op == 'Q')
		{
			int u, k;
			u = read(), k = read();
			int pp = find(u);
			int ans = search(root[pp], k, 1, n);
			if(ans == -1) printf("%d\n", ans);
			else printf("%d\n", id_to[ans]);
			
		}
		else
		{
			int u, v;
			u = read(), v = read();
			int pp = find(u);
			int qq = find(v);
			if(pp == qq) continue;
			fa[qq] = pp;
			root[qq] = merge(root[pp], root[qq], 1, n);
		}
	}
	return 0;
}