luogu3224 [HNOI2012]永无乡

线段树合并好写好调，隔壁老王的treap+启发式合并难写难调

#include <iostream>
#include <cstdio>
using namespace std;
int n, m, fa[100005], val[100005], rot[100005], uu, vv, fan[100005], cnt;
int lson[5000005], rson[5000005], sum[5000005];
char ss[5];
int myfind(int x){
	return fa[x]==x?x:fa[x]=myfind(fa[x]);
}
void insert(int &k, int l, int r, int x){
	if(!k)	k = ++cnt;
	if(l==r)	sum[k] = 1;
	else{
		int mid=(l+r)>>1;
		if(x<=mid)	insert(lson[k], l, mid, x);
		if(mid<x)	insert(rson[k], mid+1, r, x);
		sum[k] = sum[lson[k]] + sum[rson[k]];
	}
}
int query(int o, int l, int r, int x){
	if(l==r)	return l;
	int mid=(l+r)>>1;
	if(x<=sum[lson[o]])	return query(lson[o], l, mid, x);
	else	return query(rson[o], mid+1, r, x-sum[lson[o]]);
}
int merge(int x, int y){
	if(x==0 || y==0)	return x+y;
	lson[x] = merge(lson[x], lson[y]);
	rson[x] = merge(rson[x], rson[y]);
	sum[x] = sum[lson[x]] + sum[rson[x]];
	return x;
}
int main(){
	cin>>n>>m;
	for(int i=1; i<=n; i++){
		scanf("%d", &val[i]);
		fa[i] = i;
		fan[val[i]] = i;
	}
	for(int i=1; i<=m; i++){
		scanf("%d %d", &uu, &vv);
		fa[myfind(vv)] = myfind(uu);
	}
	for(int i=1; i<=n; i++)
		insert(rot[myfind(i)], 1, n, val[i]);
	cin>>m;
	while(m--){
		scanf("%s", ss);
		if(ss[0]=='Q'){
			scanf("%d %d", &uu, &vv);
			int p=myfind(uu);
			if(sum[rot[p]]<vv)	printf("-1\n");
			else	printf("%d\n", fan[query(rot[p], 1, n, vv)]);
		}
		else{
			scanf("%d %d", &uu, &vv);
			int p=myfind(uu), q=myfind(vv);
			if(p!=q){
				fa[q] = p;
				rot[p] = merge(rot[q], rot[p]);
			}
		}
	}
	return 0;
}