POJ2761 Feed the dogs

//It is made by ljh2000
#include <iostream>
#include <cstdlib>
#include <cstring>
#include <cstdio>
#include <cmath>
#include <algorithm>
#include <ctime>
#include <vector>
#include <queue>
#include <map>
#include <set>
#include <string>
using namespace std;
typedef long long LL;
const int MAXN = 100011;
int n,m,a[MAXN],c[MAXN],L,cnt,root[MAXN];
struct node{ int ls,rs,val; }tr[MAXN*20];
inline int getint(){
    int w=0,q=0; char c=getchar(); while((c<‘0‘||c>‘9‘) && c!=‘-‘) c=getchar();
    if(c==‘-‘) q=1,c=getchar(); while (c>=‘0‘&&c<=‘9‘) w=w*10+c-‘0‘,c=getchar(); return q?-w:w;
}

inline int build(int rt,int l,int r,int k){	
	cnt++; tr[cnt]=tr[rt]; tr[cnt].val++; if(l==r) return cnt;
	int cc=cnt; int mid=(l+r)>>1;
	if(k<=mid) tr[cc].ls=build(tr[rt].ls,l,mid,k);
	else tr[cc].rs=build(tr[rt].rs,mid+1,r,k);
	return cc;
}

inline int query(int up,int down,int l,int r,int k){
	if(l==r) return l; int cp=tr[ tr[up].ls ].val-tr[ tr[down].ls ].val; int mid=(l+r)>>1;
	if(k<=cp) return query(tr[up].ls,tr[down].ls,l,mid,k);
	else return query(tr[up].rs,tr[down].rs,mid+1,r,k-cp);
}

inline void work(){
	n=getint(); m=getint(); for(int i=1;i<=n;i++) a[i]=getint(),c[i]=a[i];
	sort(c+1,c+n+1); L=unique(c+1,c+n+1)-c-1;
	for(int i=1;i<=n;i++) a[i]=lower_bound(c+1,c+L+1,a[i])-c;
	for(int i=1;i<=n;i++) root[i]=build(root[i-1],1,L,a[i]);
	int l,r,k;
	while(m--) {
		l=getint(); r=getint(); k=getint();
		printf("%d\n",c[ query(root[r],root[l-1],1,L,k) ]);
	}
}

int main()
{
    work();
    return 0;
}