[POJ2104]K-th Number

#include<cstdio>
#include<map>
#include<algorithm>
#include<cstring>
#define N 100005
using namespace std;
int n,m,root[N],d[N*20],node=0,mx;
int a[N],b[N];
int ld[N*20],rd[N*20];
map<int,int>mp;
void ins(int& cur,int t,int l,int r,int k){
	cur=++node;
	d[cur]=d[t];
	d[cur]++;
	ld[cur]=ld[t],rd[cur]=rd[t];
	if(l==r)return;
	int m=l+r>>1;
	if(k<=m)ins(ld[cur],ld[t],l,m,k);else
	ins(rd[cur],rd[t],m+1,r,k);
}
int query(int L,int R,int l,int r,int k){
	if (k==0) return 0;
	if(l==r)return l;
	int ls=d[ld[R]]-d[ld[L]],m=l+r>>1;
	if(d[R]-d[L]<k)return 0;
	if(k<=ls)
	return query(ld[L],ld[R],l,m,k);
	return query(rd[L],rd[R],m+1,r,k-ls);
}
int main(){
	scanf("%d%d",&n,&m);
	for(int i=1;i<=n;++i)scanf("%d",&a[i]);
	mx=n;
	memcpy(b,a,sizeof b);
	sort(b+1,b+n+1);
	mx=unique(b+1,b+n+1)-b-1;
	memset(root,0,sizeof root);
	for(int i=1;i<=n;++i)ins(root[i],root[i-1],1,n,lower_bound(b+1,b+mx+1,a[i])-b);
	while(m--){
		int l,r,k;
		scanf("%d%d%d",&l,&r,&k);
		printf("%d\n",b[query(root[l-1],root[r],1,n,k)]);
	}
	return 0;
}