poj 2104持続可能セグメントツリー区間Kは大きく変更されない

#include
#include
#include
#include
#include
#include
#include
#define N 240008
#define M 5500000
using namespace std;
int n,m,rt[N];


struct Node{
    int l,r,cnt;;
}tr[N<<4];
int cur;

void pushup(int x)
{
    int l=tr[x].l,r=tr[x].r;
    tr[x].cnt=tr[l].cnt + tr[r].cnt;
}
inline void apushup(int o) {
    tr[o].cnt = tr[tr[o].l].cnt + tr[tr[o].r].cnt;
}

int build(int l,int r ) {
    int k = cur++;
    if (l == r) {
        tr[k].cnt = 0;
        return k;
    }
    int mid = (l + r) >> 1;
    tr[k].l = build(l, mid);
    tr[k].r = build(mid + 1, r);
    pushup(k);
    return k;
}

int update(int x,int l,int r,int pos,int val)
{
    int k = cur++;
    tr[k] = tr[x];
    if (l == pos && r == pos) {
        tr[k].cnt += val;
        return k;
    }

    int mid = (l + r) >> 1;
    if (pos <= mid)
        tr[k].l = update(tr[x].l, l, mid, pos, val);
    else
        tr[k].r = update(tr[x].r, mid + 1, r, pos, val);
    pushup(k);
    return k;
}

int Ask(int l,int r,int x,int v,int kth) {
    if (l == r)return l;
    int mid = (l + r) >> 1;
    int res = tr[tr[v].l].cnt - tr[tr[x].l].cnt;
    if (kth <= res)return Ask(l, mid, tr[x].l, tr[v].l, kth);
    else return Ask(mid + 1, r, tr[x].r, tr[v].r, kth - res);
}

int b[N];
int sortb[N];


int main()
{
    while(~scanf("%d%d",&n,&m))
    {
        //init();
        cur=0;
        for(int i=1;i<=n;i++)
        {
            scanf("%d",&b[i]);
            sortb[i]=b[i];
        }

        sort(sortb+1,sortb+n+1);
        int cnt=1;
        for(int i =2;i<=n;i++)
        {
            if(sortb[i]!=sortb[cnt])
                sortb[++cnt]=sortb[i];
        }

        rt[0]=build(1,cnt);

        for(int i=1;i<=n;i++)
        {
            int p=lower_bound(sortb+1,sortb+1+cnt,b[i]) - sortb;
            rt[i]=update(rt[i-1],1,cnt,p,1);
        }

        int l,r,k,z;
        for(int i=1;i<=m;i++)
        {
            scanf("%d%d%d",&l,&r,&k);
            int idx=Ask(1,cnt,rt[l-1],rt[r],k);
            printf("%d
",sortb[idx]);
        }

    }

    return 0;
}
/*

7 3
1 5 2 6 3 7 4
2 5 3
4 4 1
1 7 3

 */