HackerEarth Gaurav And Sub-array problem solution

In this HackerEarth Gaurav And Sub-array problem solution, You are given an array A[] consisting of N non-negative integers. Now, you need to answer Q queries of the following type given an integer K in each query.

You need to find the minimum length L of any subarray of A, such that if all elements of this subarray are represented in binary notation and concatenated to form a binary string, then no of 1’s in the resulting string is at least K.

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

const int N = 1000005;
int sbit[N];
int a[N];
int sum[N];
int func(int n)
{
    int cnt=0;
    while(n)
    {
        n=n&(n-1);
        cnt++;
    }
    return cnt;
}
void pre()
{
    for(int i=0;i<N;i++)
    {
        sbit[i]=func(i);
    }
}
void calSum(int n)
{
    sum[0]=a[0];
    for(int i=1;i<=n;i++)
    {
        sum[i]=sum[i-1]+sbit[a[i]];
    }
}
bool check(int n,int x,int k)
{
    for(int i=0;i<=n-x;i++)
    {
        if((sum[i+x]-sum[i])>=k)
        {
            return true;
        }
    }
    return false;
}
int main()
{
    pre();
    int n,q,k;
    scanf("%d%d",&n,&q);
    a[0]=0;
    for(int i=1;i<=n;i++)
    {
        scanf("%d",&a[i]);
    }
    calSum(n);
    while(q--)
    {
        scanf("%d",&k);
        int lo,mid,hi,ans;
        lo=1;
        hi=n;
        ans=-1;
        while(hi-lo>=0)
        {
            mid=(lo+hi)/2;
            if(check(n,mid,k))
            {
                ans=mid;
                hi=mid-1;
            }
            else
            {
                lo=mid+1;
            }
        }
        printf("%dn",ans);
    }
    return 0;
}