Nominating Group Leaders - Hackerrank

#include<bits/stdc++.h>
using namespace std;

#define pfin(a) printf("%d\n",a);
#define pfln(a) printf("%lld\n",a);
#define pfis(a) printf("%d ",a);
#define pfls(a) printf("%lld ",a);
#define sfi(a) scanf("%d",&a);
#define sfl(a) scanf("%lld",&a);
#define fast ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL)
#define f(i,a,b) for(int i=a;i<b;i++)
#define pb(a) push_back(a);
#define mp(a,b) make_pair(a,b)
#define ll long long
#define F first
#define S second
#define vi vector<int>
#define vc vector<char>

const ll mod=1e9+7;
const int N=1e5+5;
const int BLOCK=320;// length of BLOCK size
const int BKLN=316;// Length of array of buckets

vi bckt[BKLN];// bckt denoted frequency of frequency array of that particular bucket

int arr[N];

struct util
{
    int l,r,x,idx;
};

bool cmp(util a,util b)
{
    int val1=a.l/BLOCK;
    int val2=b.l/BLOCK;

    if(val1!=val2)
        return val1<val2;

    if(val1%2==1)
        return a.r<b.r;

    return b.r>a.r;
}

int freq[N];

void add(int idx)
{
    int bkt=arr[idx]/BLOCK;
    bckt[bkt][freq[arr[idx]]]--;
    freq[arr[idx]]++;
    bckt[bkt][freq[arr[idx]]]++;
    return;
}

void remove(int idx)
{
    int bkt=arr[idx]/BLOCK;
    bckt[bkt][freq[arr[idx]]]--;
    freq[arr[idx]]--;
    bckt[bkt][freq[arr[idx]]]++;
    return;
}

void solve()
{
    memset(freq,0,sizeof(freq));
    f(i,0,BKLN+5)
        bckt[i].clear();

    f(i,0,BKLN)
        bckt[i].resize(N+5);

    int n;
    sfi(n)

    f(i,0,n)
        sfi(arr[i])

    int q;
    sfi(q)

    util query[q];

    f(i,0,q)
    {
        sfi(query[i].l)
        sfi(query[i].r)
        sfi(query[i].x)
        query[i].idx=i;
    }

    sort(query,query+q,cmp);

    int mleft=0,mright=-1;

    int ans[q];
    memset(ans,-1,sizeof(ans));

    f(i,0,q)
    {
        int left=query[i].l;
        int right=query[i].r;

        while(mright<right)
        {
            mright++;
            add(mright);

        }
        while(mright>right)
        {
            remove(mright);
            mright--;
        }
        while(mleft<left)
        {
            remove(mleft);
            mleft++;
        }
        while(mleft>left)
        {
            mleft--;
            add(mleft);
        }

        f(j,0,BKLN)
        {
            if(bckt[j][query[i].x]>0)
            {
                int l=j*BKLN;
                while(freq[l]!=query[i].x)
                {
                    l++;
                }
                ans[query[i].idx]=l;
                break;
            }
        }
    }

    f(i,0,q)
        pfin(ans[i])

    return;
}

int main()
{
    int t;
    sfi(t)

    while(t--)
        solve();

    return 0;
}