E - K-th Number POJ - 2104

#include<cstdio>
#include<iostream>
#include<algorithm>
#include<cstring>
#include<sstream>
#include<cmath>
#include<stack>
#include<cstdlib>
#include <vector>
#include<queue>
using namespace std;

#define ll long long
#define llu unsigned long long
#define INF 0x3f3f3f3f
#define PI acos(-1.0)
const int maxn =  1e5+5;
const int  mod = 1e9+7;

int n,q,m,tot;
int a[maxn],t[maxn],T[maxn],lson[maxn*30],rson[maxn*30],c[maxn*30];

void Init_hash()
{
    for(int i=1;i<=n;i++)
        t[i] = a[i];
     sort(t+1,t+1+n);
     m = unique(t+1,t+1+n)-t-1;
}

int build(int l,int r)
{
    int root = tot++;
    c[root] = 0;
    if (l != r)
    {
        int mid = (l+r) >> 1;
        lson[root] = build(l,mid);
        rson[root] = build(mid+1,r);
    }
    return root;
}
int Hash(int x)
{
    return lower_bound(t+1,t+1+m,x)-t;
}
int update(int root,int pos,int val)
{
    int newroot = tot ++,tmp = newroot;
    c[newroot] = c[root] + val;
    int l = 1,r = m;
    while(l <r)
    {
        int mid = (l+r)>>1;
        if(pos <= mid)
        {
            lson[newroot] = tot++;
            rson[newroot] = rson[root];
            newroot = lson[newroot];
            root = lson[root];
            r = mid;
        }
        else
        {
            rson[newroot] = tot ++;
            lson[newroot] = lson[root];
            newroot = rson[newroot];
            root = rson[root];
            l = mid + 1;
        }
        c[newroot] = c[root] + val;
    }
    return tmp;

}
int query(int left_root,int right_root,int k)
{
    int l = 1,r = m;
    while(l < r)
    {
        int mid = (l+r) >> 1;
        if(c[lson[left_root]] - c[lson[right_root]] >= k)
        {
            r = mid;
            left_root = lson[left_root];
            right_root = lson[right_root];
        }
        else
        {
            l = mid + 1;
            k -= c[lson[left_root]] - c[lson[right_root]];
            left_root = rson[left_root];
            right_root = rson[right_root];
        }
    }
    return l;
}
int main()
{
    scanf("%d%d",&n,&q);
    tot = 0;
    for(int i=1;i<=n;i++)
        scanf("%d",&a[i]);
    Init_hash();
    T[n+1] = build(1,m);
    for(int i=n;i;i--)
    {
        int pos = Hash(a[i]);
        T[i] = update(T[i+1],pos,1);
    }
    while(q--)
    {
        int l,r,k;
        scanf("%d%d%d",&l,&r,&k);
        printf("%d\n",t[query(T[l],T[r+1],k)]);
    }
}